more time to bake

The issue is that we're finding that no kernel ever released has been adequately bug-free, and it doesn't make sense to hold up releasing 7.2.0 until people stop finding bugs that are still in the 7.1 series and had been in the kernel for years when 7.1.0 was released.

As far as getting a production-suitable kernel, it doesn't really matter whether the kernel before the first 7.2 one you can really rely on is 7.2.9 or 7.2-rc14, and I think your observation about the .0 kernels suggests that production-readiness improves more rapidly after Linus hands it off than before, which would mean that it would need to bake even longer if it was released later.

The real reason for not releasing a .0 right after the merge window is to avoid having .0 kernels with mutually incompatible behavior (as much as possible), since this lead to a situation where different users come to rely on different behavior and the kernel can't decide which to do. Once series that are leading to unsolvable problems have been reverted, it makes sense to nail down the feature set and move to the process where it really bakes.