If we start without M, and start with master=R2, temporary-feature-branch=R5, I expect the following outcomes:

"squash" will leave us with master=M, and the graph R1 -> R2 -> M. Once temporary-feature-branch is deleted, R3-R5 are forever lost.

"merge" will leave us with master=M, and the graph R1 -> R2 -> M, + R2 -> R3 -> R4 -> R5 -> M

"rebase" will leave us with master=R5, and the graph R1 -> R2 -> R3 -> R4 -> R5. Once temporary-feature-branch is deleted,

The first case loses the history of the code, and thus can't be what we're talking about.

If you call the second case "squash" I find that very confusing. It's also not what github is referring to when talking about "squash your commits" in the parent article, they're talking about the first case. Now, git confuses the issue a bit too - perhaps I should be labeling the second case a "non-fast-forward merge", but I'd still find that clearer than "squash without losing the history."