Doc Oc heal block not working?

Am I seeing this correctly?
I noticed in arenas lately when Doc Oc heal blocks, the defender still recovers health. You can see in pic.
I noticed in arenas lately when Doc Oc heal blocks, the defender still recovers health. You can see in pic.

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Comments
Lol
From my understanding I thought if heal block is active , any type of regeneration or healing wasn’t possible.