SXY/SAX/SAY aren’t the best instructions in the world. One 65x comparison doc in general, said they were a waste of opcode. While I agree that there could have been better opcodes added/upgraded to the 6280 from the W65C02S, they are not without their uses (albeit limited). I’ve used them on occasion; not so much as to save a cycle or three (I do that too), but as a convenient method of keeping code cut down/readable. Not unlike the BBR/BBS instructions.