I watched the video clip on Twitter that Penk referred to earlier, I'll try and link it when I find it again.
Shows the defender going up for a header with I think Bonatini, winning it but getting no distance on it so then he goes up again to complete the clearance. It's at this point that Batth comes charging in and makes contact with the player but never even gets off the ground so in my eyes it's difficult to argue that he's even challenging for the ball let alone the man being fouled.
So coming back to your comparison to a player getting wiped out in a tackle, I'd view the Bristol player as the one being in possession as he'd won the previous header and was looking to complete his clearance, Batth then comes in late and makes no real challenge for the ball but cleans the Bristol player out.