Board Thread:Manga/@comment-37224578-20181118220414/@comment-7630054-20181128214746

TKGriffiths wrote:

Also, it's not as if there's any inherent in-universe reason for the nine titans to have totally equal combat prowess. For all we know they weren't even designed for combat. If they were designed at all. Personally, I think it is sort of evolution process, given the only truly unique ability demonstrated so far is the Colossal Nuke, but that might be a product of the energy release in creating something this big. Every single other ability is present in some form in at least two titan shifters (even Coordinate is not unique, since Female has a limited control over mindless titans. Plus Zeke and his royal blood shenanigans).

Basically, I think back when Ymir's power was split, all Nine got the same pool of powers, but over years ones were used more frequently by some than the others. The former grew more efficient, the latter - redundant. Centuries later you're just observing the result of such evolution, with some powers being defined better than the others. And that bottle Eren gulped basically enhanced the 'hardening' gene he already had in his Titan, just laying dormant because it wasn't developed.