Sortie Objective B1

As a community, I would like to revisit and collaborate on this objective, as it is both the only one still marked on the wiki as "needs verification" and the only objective that I randomly fail or succeed at outside of the description soloing.

The current description is:
"Vanquish 3 Biune foes within 30 (Verification Needed) seconds of gaining enmity."

When I solo, I usually use Ifrit to kill Umbrils. I have 20 second BPs and make sure to Flaming Crush as soon as the avatar engages. Numerous times, I have killed Umbrils in 2 BPs and not gotten the chest, while other times if I get bad damage rolls and it takes 3 BPs (and thus at least 40 seconds), I still get the objective. I am unclear if engaging with my trusts or using Dia helps or hinders objective clearing. I also wondered if it didn't rely on the actual clock and instead relied on 30 'second' in game time chunks: ie if you start killing it at 7:59 and kill it at 8:05, that it might not count. Or that the 30 second kills have to be in a chain with no failed kills in-between, but that wouldn't explain why failures sometimes count as successes...

I'm grasping at straws trying to find some sort of consistency here. Any ideas? Experiences?