If you're learning guitar, drums, piano, trumpet, etc, you'll want to start playing along at about 75% speed then work up until you can play 110% faster than you need to. YouTube's built in audio time stretch makes this a painful exercise.

What's the benefit of learning to play faster than you need to? I understand wanting to play slower, but why faster?

You want to play within your abilities, not right at the very edge of them. This technique nudges the edges out.

Fair enough. Never heard this technique before. Note that such a technique wouldn't translate to other skills like dancing, singing, sawing a piece of wood. Doing those things faster I can't imagine would be of any help in improving how you do them at normal speed.

Reliability builds on skill redundancy.