the best thing about it is we don't even have u21's anymore so nobody is eligible for the U21s for three full seasons. No doubt a new definition will be snuck in at some point.

Yep. The club trained rule is mentioned in the rules but not defined. Nor does it apply to the section it is mentioned in anymore as the subsequent paragraph (where it used to detail the amount of "Homegrown" players need in a squad) is now gone.

I had to find an old version of the rules to find the club trained definition.

It also in the definition which does exist specifically mentions that it only applies to SL clubs so championship clubs cannot have any club trained players at all.