This is truer now that `git bisect --first-parent` exists. But it didn't always. And even then, there are times you find out that there is "prep work" to land your feature. And a PR just to do some deck chair moving that makes a follow-up commit easier is kind of useless. I have done prep work as a separate PR, but this is usually when it is more extensive than the feature and it is worthwhile on its own.

Another instance is a build system rewrite. There was a (short) story of the new system itself and then a commit per module on top of that. It landed as 300+ commits in a single PR. And it got rebased 2-3 times a week to try and keep up as more bits were migrated (and new infra added for things other bits needed). Partial landing would have been useless and "rewrite the build system" would have been utter hell for both me developing and anyone that tries to blame across it if it hadn't been split up at least that much.

Basically, as with many things in software development, there are no black-and-white answers here.