Monsters and Mutagenic Fog

[Alethiolet]

While playing a HOFi of Beogh in Cigotuvi's Fleshworks, I tried to mutate one of my orcish follower in all the mutagenic fog that was hangin about there, but to no result. I had read that mutagenic fog polymorph monsters, is this no longer true? Or are just Beogh's orcish followers restricted from doing so?

[kuniqs]

Mutagenic fog no longer polymorphs monsters.
It lowers their hd and defences instead. (temporalily)