Being immune to charm or immune to magic are two different things. There were mobs flagged as uncharmable in classic as pointed out in the merchants immune to charm thread that you commented on Baugi.
https://www.project1999.com/forums/s...=357217&page=3
Also, why would it be flagged slow immune when a shaman disease could slow it in Luclin? What would disease slow have to do with charm? Irrelevant.