DY: There were many Poskim (I believe R’ Ovadia included) that felt that Ashkenazim in E”Y should switch over the the S’fardi pronunciation because that’s the Minhag in Eretz Yisrael. I think the “Modern Orthodox” who say Taf isn’t a show of solidarity with E”Y. It’s because many members of the community became Frum in or because of a connection to E”Y and therefore spoke like E”Y. I think you’ll find that those “Modern Orthodox” people who have been Frum for 4 or more generations all say “Saf”. (Even the majority of Talmidim in “Modern” American Yeshivos in E”Y like Gush, KBY, etc. say Saf.)
Oh, and Krias Sh’ma is Ne’emeres B’kol Lashon so that’s not a ra’ayah.