You already said it in first post and you’re right if F(L)OSS would describe free software. But F(L)OSS describes that a part open source software is even free/libre. To describe free software with open source is redundant, specifying open source with free or libre is not redundant. That’s what I tried to say above.
But I also could explain it further: we could write FS (free software), but than it is such a short thing, that it could be everything like “Failed Security”. FS is also no term that slips as good as “F(L)OSS” out of mouth.
I did not write that those terms are good or bad. I just described why it makes at least some logical sense that they exist. On the other hand they’re also more technical terms that I wouldn’t even consider to use in conversations with common people. So we can stop the discussion about F(L)OSS anyway, because it’s outside of your needs in any case.
However, all of this has nothing to do with my other opinion, that locked and unlocked is even more confusing (for me and even more for newbies). If I speak about games (like you did inside the quote) and the “enthusiast” said “creating unlocked software” I would ask if he’s speaking about cracking games and as normal person I would loose interest after that longer explanation (in fact, people loose interest a way too fast on such topics - you can’t do a lot to improve it).
I have no idea if there is a term that is better than free or libre software. But “unlocked” is not.