My point is correct. Yes. It is widely understood by people to mean and imply multiple options, but in fact it is incorrect. The term “instead of” means TO REPLACE. It makes not ONE BIT of difference if the word “only” is there or not, unless he clarifies the meaning in the sentence (read a little bit down, at the end of this paragraph to what I mean)… It still means the SAME THING. “WASD” movement ONLY “instead of”, or to REPLACE, ONLY mouse movement. Read the sentence again, this time using the term “to replace” and not “instead of”. If he would have said “WASD & mouse” in the first part, and then said “instead of only mouse” in the second, then, yes, you would be correct. AS WORDED, it means to replace mouse with WASD.
English was the only class I received an “A” in, from grammar school through High school. I live right near UCONN campus, a state college. The meaning is implied and accepted, but is in fact incorrect. Nobody, except those like me, never even notice or care to be honest with you. Just how my wacky brain functions. But I have emailed the UCONN Dept. Of English Professor and asked her if I am right or wrong. I am man enough to admit it if I am. We shall see if she answers.