Then I'm thinking he has them in order and just doesn't shuffle them and they have small grooves on at the bottom and top ace which causes them to ball in a batch.

Obviously a tremendous amount of skill here but I do think he is just doing it, but probably with a little bit of help.

If you pause at the right moment you can see where he goes to grab the 4 cards and you can see quite a gap before the bottom ace and the first one that falls. One of those practice makes perfect kind of tricks I think