Agree with Doctah here, it is hard to judge goalies who haven't seen much time, but I watched the UVA-Army game last year and came away very impressed with Gavin. I think this is a big get for Syracuse and gives them a goaltender who has actual starting DI experience. He finished with a 60% save percentage in that Army game. The following week against Loyola he wasn't nearly as good, letting in 12 goals and only making nine saves. But he's still bringing more to the table the current roster of SU goalies, and he's still only a sophomore.
Again, really hard to judge backup goalies, but neither Thompson or Katchadurian showed much in mop up duty last year. They only faced a combined 11 shots last year, but usually with backups, when they do see time, you can usually see something that gives you hope. I didn't get that sense with either Thompson or Katchadurian last year. FWIW, in 2020, Desko did give them both a shout out after an impressive scrimmage performance.
Like the quarterback position, only one can play on the field at the same time - if UVA happens to have two (or three) really good goalies, it doesn't change the fact that the "second best" could still be really good and would make another team better.