I don't know if it applies in this situation, but certain cases make sense to fork instead of patch. If they are including features that are orthogonal to general MySQL feature set, it shouldn't be patched.
Considering their size and unique requirements induced by that size, I imagine a lot of these changes do not apply to small MySQL installations running WordPress (and in fact may be highly detrimental).
I think all of the changes pretty much do apply generally, but for us it's easier to go ahead and publish publically to be able to pass these changes upstream, rather than pass them off privately and wait potentially a year or more to get them back in a public release.
We want to be able to collaborate with Percona, Facebook, Google, MariaDB, etc., on some of the actual changes, to make things better for everyone. This is the first step towards that goal.
Considering their size and unique requirements induced by that size, I imagine a lot of these changes do not apply to small MySQL installations running WordPress (and in fact may be highly detrimental).