Thrall Sundering integration with Twilight Dream bugged?

So I play Malfurion a decent amount and now that Thrall started to be very popular I've noticed on 3 different occasions that after I've hit Thrall with Twilight Dream he has been able to cast Sundering about 0.5-1 second after getting hit with Twilight Dream and still being silenced (no cleanses used). I've checked the replays to confirm this, it might be an intended interaction, but as far as Im aware, every single ability with a cast time can be interrupted.

I dont know if Im going crazy or if something's off, but has anyone else experienced this?