There is very little doubt that for non-rotated flats and flat corrections centered on good light panels, the current math works very, very well indeed. No changes needed that I'm aware of. There has to be some accommodation for minute-to-minute variations in light panel brightness, which are real even for high-end panels. I'm getting vignetting corrections good to 1-2 millimagnitudes (0.1-0.2 % flux), every night for years, without even trying very hard. To hold constant the exposure time per session, per filter, giving up the constant flux advantage, would make for a change I'd need to see tested. As an new option in ACP Preferences it might be fine.

I wouldn't know whether this extends to rotated flats and flat corrections; to figure that out I would have to know the excruciating details of how the flats are taken, combined, and applied. This complication is one of a dozen reasons why I've never gone near a rotator.

Arne might have some insight on flats through rotators, though I don't know whether he's ever used one, either. The APASS project doesn't, and I'm pretty sure AAVSOnet doesn't either, at least not up to a year or two ago.