It appears that the Grand Champion's "free" training (and any of the "free" training in the game) can kick your skills over 100, but doing so is pointless, as your skills do not gain any benefits past level 100, with the possible exception of Athletics.

Is this correct?

The only skills beneficial after 100 are athletics and acrobatics. That I know of.

Either way its still free points.

Just wondering if it was worth not completing that quest until I maxed out Athletics and Acrobatics. If there's no practical difference, then it's not, but if a skill of 103 is actually better than 100, why not?