Psyker Penance Malleus Monstronum + F ability = Failed penance?

Currently the description is the following:

“While on Heresy threat or higher singlehandedly kill a Monstrosity where by all damage inflicted is done by you and all damage inflicted is done by brain burst”

I tried to get this penance done, coordinated with a team in voice comms, seemingly everything went according to plan but I didn’t get the penance. Of course there is a good chance that some teammate or I hit the monster with some other attack, but my teammates were far away from the boss so I’m a bit confused.

Key thing here is that the description says ALL DAMAGE. I did use the Psyker F ability “Psykinetic’s Wrath” aiming at the boss. The ability does no damage, however, does this still mess up the penance? I would like some clarification here, because to me the setup for the solo kill seemed perfect otherwise.

I believe it does indeed count as damage (it just does 0). However, it’s not just that.

Barrel explosion? Fail
Bomber/flamer puts fire down? Fail

So, assuming you get one to spawn again, good luck. You’ll need it.