I think he was referring to the limitations placed on cards that extend into the front GPU cut-out. According to ncases.com, cards that take up more than 2 slots are limited to 11", and 308mm = 12+".
Yeah thats what I meant though I can see how my wording is a little wonky. Basically the longest part of the card also happens to reside in the area that occupies the 3rd slot which is limited to a much shorter length than the other two slots.