Should Totemic Summons be Immune to Stun?

I've just run into the party below Candlekeep, and one of them used Darts of Stunning on a Spirit Lion (cast by a Level 10 Totemic Druid). I was surprised to see that it was stunned.
This is BG:EE up-to-date with no mods.
Is this expected behaviour? Lots of former posts say that the spirit animals are immune to stun.
This is BG:EE up-to-date with no mods.
Is this expected behaviour? Lots of former posts say that the spirit animals are immune to stun.
0
Comments
https://forums.beamdog.com/discussion/comment/908770/#Comment_908770
https://forums.beamdog.com/discussion/31754/totemic-druid-summon-stats
It's amazing how widespread this info is, considering it's wrong