Soul sand and soul soil still generate below the Nether roof

Cannot reproduce. As always, please provide the seed..

Here it is (New screenshot)

Just as a side note, it's easier for people to reproduce your issue if you add the seed and coordinates as copy and pasteable text to the ticket. See MC-125675 for a good example.

Hmmm. This issue seems to be fixed in 20w48a. I've attached a video which proves this.

Unable to reproduce in 20w49a as well.

I'm unable to reproduce this in the current release.