I bought a cable that claimed to be CAT6A and refuses to link greater than 5Gbit over 10m.
On the other hand a very thin flat cable I bought prior that claims CAT6, links up at 10Gbit fine, and it was that one I was replacing as I had my doubts considering how thin it is.
I think there's probably a better chance of getting 10Gbit on a CAT5e cable than a CAT6, as they are less likely to be lying about actually being CAT5e than they are CAT6.