I think the big gap in rec tennis is 3.5 vs 4.0 - and not 4.5. FWIW..
4.0 league players are guys who LOOK like very good tennis players if you see them in person and don't watch a lot of pro tennis up close, IMHO.
Anything below 4.0 tends to be variations of hackers. I think below 4.0 almost anything 'works'. You hack your way to winning tennis with pattycake serves and groundstrokes built on gravity based 'moonball slices'.
4.0 actually is the 'magic' number because 'junk' doesn't work on legit 4.0s IMHO. Sure they can lose to an actual counterpuncher.. But these guys don't lose to people who have awful mechanics and dysfunctional 'footwork."
All that being said that doesn't mean people who don't play at the 4.0 level don't know tennis..That's the silly part of this thread.