Ok, but why do goalies tend to have a later peak? Reaction time and flexibility are at their best when younger- is it just because goalies make no sense? I’d think athleticism trumps experience with that position, but obviously somethin else is going on. Explain.
My thought is it's because a huge part of goaltending at the highest levels is mental. It's not enough to be super quick and flexible if you're a little out of position because you didn't read the play correctly. Or if you get a little rattled every time you give up a goal. I'm not sure if it's experience or physical/emotional maturity or what, but it takes most guys some time to be able to avoid those mental lapses that can lead to weak goals. Just 1 weak goal every 100 shots (~3 games) is a .010 difference in SV%, which is currently the difference between 4th best in the NHL and 18th best. Much worse than that, and the NHL probably won't have much use for you.
The flip side of that is that a lot of the guys who do actually figure out the mental game also tend to start breaking down physically starting around 33, and their play starts to decline. Obviously, that's not always the case and older guys can still be very effective, but often enough that it's a gamble to pin your hopes on a goalie over about 33. These ages come from a study done on NHL goaltending, that I unfortunately can't currently find.