He can't.
The trait in mid combo on the ground isn't designed that way. For instance, if I fire a Batarang after the trait hits the rang will combo, but, I cannot combo Batarang then trait then something, the opponent will be able to block.
So let's say the trait was unblockable if timed perfectly after a Pushblock, even if it hit, you wouldn't be able to combo. It was one of the first things I tired to do with this game. It doesn't work. I wish it did.