My concern is that historically some of the conflict over bcachefs was because work on it touched code outside the filesystem area. If a year from now they show up and say "okay, here's the new bcachefs code that's 100% formally verified and has zero bugs and is good to go!", then it still could fail to get merged because they rewrote parts of (say) the block device system and the maintainers of that part of the kernel don't like the changes.

Hey, the block i/o subsystem is at least connected! Kent also wrote a brand-new locking system: https://lwn.net/Articles/755164/

I didn't forget about these things, but I was under the impression that they had been resolved one way or another.