While I get that this discussion is taking place in the context of contentious CoC debates in other projects, what I don't understand is why this is a big deal in the Linux case.

Yes, people have been complaining about Linus' occasionally unambiguously abusive behavior for a long time, this genuinely seems like Linus had a bad few days, was pulled aside by some subset of the maintainers, and came to the conclusion that he should make some changes to his behavior and to the community of the project he controls.

I didn't see any threats or endless contentious debate derailing the project, so I'm genuinely struggling to understand why people are upset about this. If his previous behavior was acceptable, surely his new behavior will be acceptable as well?