This mob does it’s fire and ice attacks even when frozen for the whole fight.
I know some mobs (like Yruns cage) can cast spells in the non-frozen-gaps in the fight that continue their duration and that mobs can have their attacks interrupted - even bosses - by being frozen.
But Argolos always does it’s 2 attacks regardless and the freeze function of interrupting attacks is having no effect. Happens every time.
Edit: Having looked at the fight a bit more closely, the fire and ice attacks occur at 66% and 33% health … so I’m guessing it’s an in-built mechanic?