Some will say to this "you should go to the lab, no one HAS to tell you anything". And it's true that no one HAS to share information.
Shame on everyone who keeps these secrets.
Damn I came here late, my reply is less relevant now.
Firstly, the first thing is completely true.
'Withholding information' is a strong term that somewhat implies that the information can not be gotten easily and that you have some sort of right to it, information that you can't get unless you actually know that it is being hidden from you. For example, a shop that has a secret policy of no refunds on a certain product brand is not something you would actually know unless asked. If you asked and they say they don't know, but then confirm it after you've bought it (and they deliberately played dumb about it to secure a sale), they withheld the information deliberately since you have a right to know.
If there is a sign next to the product and you ask a new employee if it allows refunds and they say they dont know, they are not withholding information. The onus is on you to find that out, even if the employee should have known, the point is information was available, they didn't withhold anything, you just didn't find it.
An opposition team in a sports match can have a playbook, you ask to see it. They can withhold it because you have no right to it. There is significant time and money invested into it of which you have exactly no claim over.
In the case of smash, every player has the right to this information however unlike the first scenario, you can quite easily get the information. If you ask a metaknight main 'hey tell me what % DA confirms into a kill on ROB' and they say 'no that's secret', then you say 'grow up idiot' and go on training mode and spend a few minutes finding it out. if they say 'I don't know' and they are potentially lying about it, go on training mode and spend a few minutes finding it out.
Them not telling you is not 'withholding information' since you can easily get it yourself.
If the information was somewhat difficult to get and took a lot of effort, then your right to such information is far less. This is why consultants and lawyers etc exist. The information they have took a long time to get and you don't deserve it for free, because it cost them many hours and $ to get it. Even so, they are not 'withholding information', even if it is the sort of information that can save you going to jail, because you dont deserve it for free.
The point is, calling what MK mains are doing as 'withholding information' is too strong a term to describe what they are doing. What they are really doing is immature and dumb. Its not even unsportsman like, because it is stupid 100x over before it becomes an issue of 'fair'.
Now that that is out of the way;
People who withhold such information even when asked, are pathetic and are usually bad players. Remember the difference between choosing not to tell people because they werent asked, and actively saying 'no' when asked.
I got downvoted for this on reddit but its true. In every smash scene I've ever been to, and I've traveled a bit, the types of people who try to hide information from their opponents are bad, mid level players at best trying to get any advantage they can. Meanwhile, the players who teach the mid level players what counterpicks to use, how to DI out of combos and how to stop their tricks are always top of their scene. Is it any wonder that Zero spends so much time and effort teach, training and making guides to show people how to beat sheik, and he remains the best in the world?
Its simple. Because he knows that relying on 'hidden' information in order to win is going to make him a worse player. Eventually this information is going to be found out and he is not going to be caught on the backfoot, unable to adapt to someone who figured out his tricks from a lab. Why waste precious tournament practice time using an unreliable technique that will get exposed in the very near future when you could have been adapting for the next event. He only wants to know the best possible way to play and I can 100% guarantee you that the best players never rely on jank to win. They are prepared to win and know that playing in some sort of easy-win bubble will never last. They don't want unreliable wins today, they want guaranteed future wins and that comes from outplaying your opponents, you will never get better at the game if you don't force yourself to improve.
I don't believe Abadango is withholding information because him not telling people is remedied by people spending a few minutes in the lab and find out for themselves. What it is however, is stupid because its not going to last. People know the threat of Metaknight and are going to research for themselves. In all the time he, or anyone else, has spent hiding or lying about this information, they could have been learning to adapt to future playstyles where people dont fall for that jank. In effect, every match he plays and relies on not telling people anything and wins, sets his further back than any metaknight who tells their opponent the %'s, and still wins.
They can play dumb all the want, its a stupid tactic that NEVER lasts and sets them further behind the opposition.
I play Mewtwo, I could tell fox mains that if they reflector, jump and reflector again it refreshes it and actually guarantees a KO on me, instead of killing them at 0%. Now tell me, in a tournament situation and I going to gamble my stock on the opponent not knowing this, or would I learn how to play the matchup at a 2016 level and beyond, knowing that my jank is going to get me one cheesy win and then act like a smug idiot for people not knowing and they learn this matchup trick immediately after?
The people that hide information are a joke and should be laughed at, because their immature and stupid playstyle is setting them back while others around them improve. They can get their lame win for now, but it wont last. Unfortunately their stupid attitude is an affliction for life. Pity them.