When a battlecrasher replaces a troop at the beginning of a battle it technically counts as one of the enemies being killed, and any traits or talents that apply “upon enemy death” will activate. I think this has been going on since the beginning and is intentional (i.e. it’s a feature, not a bug).
Side effect of the side effect: during battle crasher events, 4x Lust teams can trigger three times. So you can totally ruin somebody’s PVP day with a joke team, killing one or two troops before they get a turn. (This isn’t the reason I stopped PVPing—it’s antagonistic, but not in the same way as Life and Death Orbweavers.)