It's because they outsourced the work for the CG like crazy at the last possible minute so they could rush the game to store shelves. There were probably something like 2 or 3 different people making the various scenes in the CG where Sephiroth kills Aeris, so some inconsistency is bound to happen.
Also, the quote I mentioned isn't a bug, it's just a screw up, much like "off course!" I definitely agree that the translation team for FFVII did a terrible job and should have been fired. It was at the same level of bad as FFIIus's cheesy translation. It particularly irks me that practically nobody raises fault with FFVII's translation, but the Woolsey bashing bandwagon is crowded to overflowing.