You miss understand Andy.

Lita is talking about the last hit on baal/cerb before he goes into lottery mode. Whom ever actually causes the fight to change doesn't get credited for their last round.
This isn't about the 10mil final hit. Its about missing out on damage dealt to the main 50mil/250mil monster. In some realms missing that one last round worth on the leaderboard is the difference between 1st and 2nd, or 3rd and 4th.