In stacked diffs system, each commit is expected to land cleanly, yes.

But isn't that why you would squash before merging your PR? If you define a rule that PRs must be squashed you would still have the per commit build.

	▲	steveklabnik 32 minutes ago \| parent [-]
		Squash merge is an artifact of PRs encouraging you to add commits instead of amending them, due to GitHub not being able to show you proper interdiffs, and making comments disappear when you change a diff at that line. In that context, when you add fixup commits, sure, squashing makes sense, but the stacked diffs approach encourages you to create commits that look like you want them to look like directly, instead of requiring you to roll them up at the end.