So, I had previously noticed that the Etelia gene Ice Heart lists every kind of stun in the game it defends against, except freeze, wind gust, and now, shock from Dita. However, I'd assumed that Ice Heart and its counterpart Determined in normal pets both defended against all stuns. Until my Etelia was stunned by a roc with Massive Wings in the Arena today. 

While Ice Aura and Divine Beauty both state in the description that they are negated by Determined (and thus, also by Ice Heart), Massive Wings and Blizzard do not. Is this stun intended to be unblockable?

Yes, this is how it is supposed to work. The idea is that Determined as a brain gene works on effects that involve senses and will. Ice Heart is the same, just with a different location to spare brain slot for other useful perks. These traits don't help against direct physical knockout.

Okay, makes sense. Thank you for clarifying.