when in pre 12.2 it was possible to use Volume effect with any HDRi freely.
What if volume effect is not wanted for the HDRI?
It was no problem to set it to zero value then. So we use this "bug" in all our scenes to enhance aerial perspective and all scenes now unusable in C13. It's unfortunate. No way to use it as "legacy" mode?
I get that it could have been used as a feature, but what if you have two sky maps, one with volume and one without. In that case the volume would affect the other sky map and HDRIs. It is a clear bug which is now resolved.
I am not sure what your workflow is, but I would recommend fixing the scenes so they follow the fixed/correct behavior, as you open and decide to migrate them to v13. Hopefully the tweaks are not much. E.g. there can be new features coming to sky map and supporting this "feature" would possibly affect the new ones too, which is definitely unwanted.