As one who did a spell of production test work, this was one of the "boxes" that was required to be ticked. At max diff all bleeds would be selected to off and the increase in cabin alt (decrease in pressure) would be measured over time. It was not in any way an "ear popping" experience.
Regarding the emergency bleed air fitted to older types, and maybe to some still current, it is indeed unregulated, and of the warm kind. Many schools teach that it is extremely hot, and tell tales of pax emerging from the cabin after landing wearing nothing but boxer shorts. Having relied on it once in an old straight wing Citation, I can vouch for the fact that such stories are exaggerated. The cabin gets warm - perhaps a bit too warm, but unfortunately for me at least, the three females in the rear did not feel compelled to stip down to their underwear!