What's the problem?

Only clear bug fixes are wanted at this point to make the next release candidate(s) as small as possible. In this case, the PR contained some cleanups.

More changes can mean more regressions. The goal is to stabilize the master branch so that v4.13 can be released.

Some of these are large changes that are recent enough that it's impossible to vet them to Linus' standards.

4.13 is due for release probably this week. Linus cut -rc3 a week ago, which was small, and nothing serious have been heard. Normally only critical fixes would be merged this late which might warrant another rc, but this is Ted T'so, a wizard who has been involved in Linux since before it had networking, so his opinions have merit.

In general we always get to -rc6 to -rc8 before we do a release, with perhaps -rc7 being the most common. Since the merge window (before -rc1) is two weeks, this translates to a two month release cycle. So using a time-based release cycle paradigm, -rc3 isn't _that_ late, although as I acknowledged in another comment in this thread, it was a bit marginal.

(And by the way it's "Ts'o", but the wrong spelling is all over the Internet at this point.)