American Chareidi Sphardim are just about as likely to know Yiddish as Litvishers. Why has nobody brought this up? This isn’t a Ashkenaz/Sphard issue. This is just the usual wacky, Tzionishe suspects making a deal out of nothing.
And, saying something is “Jewish, but not Yiddish” is like saying something is “German, but not Deutsche.”