[setr]

They would be less "fluent" than otherwise. It's a scale, not a binary switch.

It would be the difference of trying to communicate about movies between someone who has only ever seen marvel films, and someone who watched say the entirety of the criterion collection. Or the difference between technical sales and engineers. It'd be fairly meaningless to give them the same label -- one is clearly capable of a more advanced communication on the subject than the other, if only because they've experience a larger subset of the subject.

Of course, you could also play the living hell out of a single game and be extremely fluent about only that one game -- which is clearly different than someone being fluent about games in general. We wouldn't expect someone who only ever played SC2, even if he had put 2000 hours into it, to have anything notable to say about FPS games and RPGs.

As you've opined, the marker of when you'd be considered a "gamer" vs otherwise is an arbitrary meaningless distinction, a random line drawn in the sand, but that's why "fluency" is trying to be introduced as an alternative.