The best player in MY region is a Meta Knight main, so I know what I'm talking about. The perfect pivot bair out of dthrow isn't exactly reliable, so I think you're putting too much stock into it (plus, I think you can also tech the bair when you land). And dthrow is completely worthless at even moderately high percents, so it definitely shouldn't be S tier.
About Lucas, you can SDI out of his nair, so some of his dthrow combos aren't guaranteed. And if this infinite is as easy as you claim, why do we never see Taiheita do it? The only player I've ever seen do it in tournament only managed to get two footstools before he messed up. Lucas's dthrow is pretty much exactly as good as Robin's, so they should be in the same tier.
Now stop acting like a condescending *******.
Theres some special property to the bair that makes it untechable, im pretty sure. Not certain though, im only basing that part off of my smash corner and something i vaguely remember reading.
The PP Bair isnt really all that difficult, i can do it rather consistently and im not even a MK main. Tyrant occasionally goes for it, as stated earlier (they backed it up with links too). Over time it will probably become even more common. It isnt used that often though because the difficulty makes the risk/reward ratio complicated.
If you know as much about meta knight as youre saying, you wouldn't have made so many plain false statements about him and his Dthrow combos.
"At low percents he only gets dash attack" wrong. Thats only on fast fallers or as a DI mix up. Its also a pretty bad option.
"At mid percents he only gets Usmash" also wrong. Usmash stops working after low %, its one of his weakest followups. Also at mid % he can do his latter combo.
Even if your #1 PR is a MK main, that doesn't mean youve watched them play and played against them hundreds of times like i have with mine.
Alternately to PP bair, at 15-35% MK can:
Dthrow > RAR Uair > FF bair > Dtilt x3 which is a much easier jab lock that does the same thing. Also you keep ignoring MK's latter combo, which Dthrow is a viable starter for. Even if it doesnt kill, it can net 35%+ damage. However,
it has the potential to kill players off of a grab at as low as 25%. Kind of a big deal.
Now onto Lucas.
First off, only some characters can SDI out of the Nair reliably, second Lucas can follow the SDI. As for Taiheita, i have no idea how often he goes for the footstool (we should really stop calling it an infinite, it technically isnt). I dont watch him play but i find it hard to believe he never ever attempts it, but either way people play differently. I already told you the Lucas main in my region goes for it constantly and it works. To be fair, there are certainly characters who are immune to it.
If you arent counting MK or Lucas as S tier, I'd be interested to know what you think makes the other S tier characters so much better? ZSS is actually worse than MK and Lucas imo. And mario, although reliable and easy, cant combo at high % and is limited to escapable Utilt strings at low %.
Also the reason the person only got two footsools is because its not an infinite. The combo can only be repeated once or twice before theyre too high up to land on their backs for the jab lock.