@vbabka and @ljs, that "Are people putting things in linux-next that they don't expect to send to Linus? That seems like the greater problem." from @kees reminded me of a question you might be able to help out with:
From a quick look it seems to me that the "mm-unstable" branch is in -next (via "mm-everything"). Does that contain stuff for the next merge window only, or more experimental stuff as well? It looks like the latter to me.