Thanks! I do know all that. Just one in a long line of Ashkenazi bastardizations of לשון הקודש. The way I grew up, we said things like keynahora for קיין עין הרע and shaleshudis for סעודה שלישית. Yontef for יום טוב was right there with these.
I was honestly pretty surprised (and amused) by how much pushback and confusion there was over this editorial decision. Reddit had a nice long discussion about it.
If my great-grandmother could spell the English word “hat” as עט in Yiddish, I can spell יום טוב as Yontef. Wontfix :)