The Gemara also says:
???? ??? ???? ????? ??? ???? ?? ??? ???? ???? ????? ????? ???? ???? ???? ??? ???? ????? ????? ??? ?? ?????? ???? ????? ????? ???????? ????? ??? ???
Does that mean that anyone who doesn’t have his cash in hand or trivide his wealth is violating a chiyuv d’rabanan? The Gemara in Berachos knew of the word “????” and chose not to use it. There are differences between the Gemara’s different expressions – see for instance the Teshuvos Maharil siman 57:
http://hebrewbooks.org/pdfpager.aspx?req=1145&st=&pgnum=40
So I don’t think one can definitively prove from the Gemara that shnayim mikra is a bona-fide chiyuv (especially in light of the other sources mentioned above). However if you want to argue based on the lashon of the Shulchan Aruch, that’s a horse of a different color, and I would find it a lot harder to argue that “???? ????? ?????” is not an obligation.