This logic goes in tandem with PSing Falco's lasers.
The timing isn't what's hard. What's hard is knowing when and where the Falco will laser you, and if you always know exactly when he's going to laser, then you're not playing a very good Falco.
Same goes for YL, if you're always catching YL's crap then you know when he's going to throw it, which means he isn't thinking, which shows that he isn't much of a player to begin with.
I'm afraid the same does not go for YL. Falco's camping ability is far better, as his lasers have a faster rate of fire, fly faster, have no distance limit, and have no lag. Both characters are of about the same in horizontal speed though.
YL has slower moving projectiles that have a lot of start-up lag and limited range, its honestly not very hard to see a boomerang, arrow, or bomb coming at you (except at point blank, at which case YL is screwed anyways).
Also, reflexes to animations =/= prediction, although it isn't very hard to predict what a YL will do with bomb in hand.
Not to mention psing falco's lasers is like 10x hard than nairing or catching yl's projectiles (for me at least).