If you look at any old US army training films back from when men were men they all teach you to shoot with a "chicken wing" stance like in pic related.
The new way teaches you to not use any bone support and be a worse marksman so you can get a little bit of protection from your gear.
WW2 and Vietnam produced millions of fucked up people who organised in biker clubs: https://www.youtube.com/watch?v=wId4VZtgW3M
The new ways produce cuckolds whose wives get fucked by BBC while they're away: https://twitter.com/Tabarius/status/875131503549837312/video/1
It's up to you to choose which one you want to be.
tl;dr not chicken-winging makes you a cuck
it works better for some rifles
others it works like shit
i'd guess it has to do with the length of pull