>One other possibility is that I know what scroll lag is, don't see it in Firefox on my devices"
Yes, that's "one other" possibility.
Now, can we also entertain the possibility I suggested as something that one can't just rule out in advance, and that one would be OK in suggesting could also be the case?
I don't know you, have not met you, and I don't speak about you as a person. I made a general observation about what could be the case when someone says what you said. Another commenter also corroborated having seen this in the wild (assuming it even needs corroboration). It's hardly something that doesn't happen. And because I'm a somewhat insulted by your tone, notice how I didn't even said anything about you directly. I wrote:
"Don't forget the other possibility: someone using Firefox having internalized this lag as "normal behavior".
The rest, you brought into this. Enough is enough. Over and out.