MrSarahLevine613, What you are saying about yuhara applies to covering the head with the talis but not about wearing it. See the MB I referred to before 17:10.
Rav Schachter seems to say, in explaining why single man dont wear a tallis at all in some places, that it is connected to yuhara. (I dont disagree with your citation. However, i am pretty sure that is NOT what he was limiting yuhara — in this context — to just covering your head. I have to go back to make sure i heard him correctly — but i think i did). His point in that part of the shiur — as is the point of this thread — was to figure out where this minhag came from. He gave two reasons as i wrote above.
“was to figure out where this minhag came from. ”
No reason to construct theories; it’s an explicit maharil.