I don't think you understand, if CF or someone low tier had this technique I could see it being banned. Besides, MK has very few real AT's. Most characters don't (depending on what you call an AT). They're not banning this because it would make MK specifically too powerful, they banned it because it would be broken on any character. A technique that makes you completely invulnerable for as long as you like should be banned period, unless you can limit it reasonably, and at this point in time and in the near future it looks like there will not be a reasonable way to limit it other than outright banning it.
I think what they meant is that if you were to allow it, you would have to define stalling through this technique. Making very specific rules on a technique (Repetitions, Duration, etc) is not only usually hard to upkeep/enforce, but they also attract a lot of subjective views since it IS hard to define what stalling is. Some people say that running away period/at all slows the match down and delays play, while some people think that running away is fine but that Stalling would be something like edge camping or abusing something to stay invulnerable completely.
For example, let's say you allow someone to use it for 5 seconds maximum before they have to stop. Someone would probably ask why not be able to use it for 10 seconds, 15 seconds, why pick/choose a specific time length? That, and now what do you do if someone calls you over and says their opponent used it for more than 5 seconds? If you want to be able to reasonably upkeep your rule, you would need a "referee" on every TV with a stopwatch. It's not wise to have a rule involved that is hard to enforce unless u have a rule for like the safety of players that is necessary or something.
So since you cannot reasonably define stalling with this technique, and it is indeed powerful if left unrestricted, then the best option is to ban it. U obviously cannot completely allow it, and at the same time there's not a good way to define a good boundary for this.