Tried to do this in a creative world, to test out a potential build for a survival thing.
30 minutes of rolling new runefused and netherfused gems later, I have gotten every other rune that is not Immolation.
Don't know if this is a bug, or just pure horrible luck, or the effect was removed (highly unlikely because the description still exists in both the wiki and the Runic Grimoire.
There WAS a rework in 1.55.0, maybe that screwed up the drop rates or something idk?
Is there a command to just give myself the rune?

Using 1.56.0, 1.20.1 on Fabric.