Never done it by GM fiat, no. (Is it just me, or does that sound like some kind of automotive joint venture?) Done it several times as natural and reasonable consequences of PC action, though. Or natural evolution of the campaign concept as it unfolds.
Well, in my OP, I do concede that natural transitions are fine.
Temporary switch-ups are fine (temporary assuming the PCs fix it)
Consequential switch-ups are fine (you do the crime, somebody gonna make you pay).
But it struck me as "not a best practice" to present Campaign X, but its really a 1 session transition into Campaign Y.
As with any "don't do this advice" there are likely examples where a GM has pulled it off and done it well. My consideration is that "don't do this advice" is for everybody else, and should only be ignored by GMs who actually know what they are doing.