Hard disagree here. GitHub does encourage this sort of thing, but even there for my PRs to be easily reviewable, I like to keep my commits organized and with good messages explaining things. That way the reviewer can walk the commits, and see why each thing was thing was done.
I also like it for myself, when I’m going over my own PRs before asking for a review - I will often amend commits to ensure the work is broken down correctly, each thing that should go together, does.
In a way, stacked PRs are just a higher-level abstraction of this too - same idea, keep work that goes together in the same place.