Curious about the 2 healer team tho... How's it fare vs lightning britzu?

Im a bit curious about his passive, and could not find any info on it.

Deidaras passive about getting crit rating for every unit in the field that dies (up to a maximum of 80%).

Lightning Main has the same description in arena prowess but without a limit (only counts towards ninjas dying, not clones/summons).

Does this mean Deidara only gets boosted when a ninja dies? or is it just a case of "let's not work extra to come up with a proper explanation" on this ability? can't really see the use of his passive goin to 80% if it only counts towards ninjas dying, and not his (or any other) summons...