"How can you possibly say that at age 13 you wont learn how to get better as a skater??"
Easy. It's backed up by tons of research from Skate Canada and the Team Canada, as well as ADM. The window of optimal trainability for boys for skill training -- things like skating skills and stick handling -- is between 9 and 12 years old, so I'm being generous by stretching it to 13 or even 14. It's true in soccer, in skating, in gymnastics, in baseball. Pick a sport.
Can you pick up new skills after 13? Sure. Will it take more work and more hours. Yes. Will those skills ever be as fine-tunable at 18 or 24 or 30. Possible, but doubtful.
By age 13-16, boys in the window of trainability for speed and power. It makes sense. Their muscles are growing, lungs are getting bigger. There are other windows of trainability for stamina and strentgth, as well.
Again, can you add or improve. Sure. But it's going to take more and more time and effort with more varying results.
This is why cross-training and being a multi sport athlete is so important for kids. Different sports and different kinds of sports hit the "sweet spot" for each window of trainability without making it a chore by going to the gym or doing a billion add-on clinics.
For example, with skating, learning to do fine-tuned one-foot turns -- a real advantage when changing direction and using edges to build speed in tight corners -- is something kids pick up easily as young teens IF they've had a good base in skating instruction all along (and that's NOT just skating forward fast, if you want to do that, just take up speed skating). But try teaching that skill to a 16 year old who doesn't have good one-foot edge control, looks down a lot while skating, can't skate backwards strongly, turns like a battleship instead of a jetski (most kids in this area AA and below) and it's going to be a lot harder. Try teaching that skill to a 20 year old with marginal skills, and it's going to take a year or so of dedicated training to learn.
Again, you want a kid who can just skate forward fast? Sure, I can do that, and I started skating at 40. But the kind of fine-tuned skills that kids from countries like Sweden, Canada, Russia or places like Minnesota and Michigan have -- places where kids are born on skates and bring hockey skates to recess? In PA, you need to work at that, and yes, the 9-13yo window is your best bet. And for intents and purposes of "I live in PA and want to skate in the NHL" trying to learn strong edges, turns and fine-tuned skating skills to build upon as later teen, the deadline is 13. If you hear of someone who made it to the NHL and just started purposeful skating training, not power skating, but skating skills training, at 14 or 15yo, that person is an outlier among outliers. It's not the safe bet and I'd encourage that person to just enjoy the sport and pick a beer league team to have fun with.