One W101 Central, it actually tells you that it places a Quench on all enemies after the attacks. The combo of damage/stun/dispel must've been bugged somehow and only placed a Quench after attacking instead of both Quench and stun.
Just tried it again, and No it still does not stun, it only quench. I am talking about Fiery Giant spell from the Deck of Immortal Might, and not Lava lord.