t's like saying that the world chess champion defeats his opponents because they have a "mathcup issue" with him
Actually, the fact that you say this about chess means that you literally have no idea what you're talking about when it comes to tennis. Let alone about chess.
Matchup issues are very real in all sports.
But age is always a factor when you get over 30 in this sport. Movement is everything in this sport. Everything else follows from movement. And if you're a step slow, everything else sucks.
Where you are correct is that Federer didn't lose this because of a matchup issue. He lost it because he's slow.