Yep, at my best I was sub-13 with a 7s PB, and I don't know full OLL so I consider myself 2.5-3LLL. I'm not particularly efficient or have high TPS so I think it's entirely possible
Yeah it could be, but it might be dependent on which cases too maybe? I don't even know how many OLLs I know/don't know since I've stopped learning new ones a while back. What's funny is I thought I knew most of OLLs so I considered myself 2.5LLL and then when I actually counted I've only learned about half, so maybe for that person that counts as 3LLL.
I just learned the ones that were easier to identify first. So maybe if that other cuber decided to learn ones that give them better efficiency, or higher probability of being used, then maybe you can shave off a bit of time.