That sounds incredibly frustrating, and you’re right to be annoyed when features don’t work as expected, wasting your time.
The issue with colored light function textures not affecting volumetric fog (and losing shape detail within it) is usually a performance-related limitation. The calculations for volumetric effects often simplify the incoming light data, skipping complex texture lookups within the volume itself.
Regressions (old features breaking) can happen in complex software when changes elsewhere inadvertently impact them. It’s a common, though aggravating, part of ongoing development. Make sure to report it officially if you haven’t already.