Is a stereo amp, when bridged to mono, by definition differential?

I've been reading about amps and the seemingly endless choices that designers make, and found myself wondering this, but haven't been able to find the answer. It would seem, if I'm correctly understanding the definition of differential, also called push-pull, that bridging the two sides of a stereo amplifier would, by necessity, be creating exactly this topology. Unless I'm missing something, of course, which may well be the case.

Thanks to those who understand such things much better than I for any clarification.

Also, those who'd rush to weigh in about the likely sonic benefits -- or detriments -- of such arrangements needn't bother, as that's not what I'm wondering about.

Thanks.

-- Howard