When using the BIS revice system the respawn eventhandler fires immediately a player is killed. It then fires again when he respawns.
Note, if the player selects respawn from the escape menu, it doesn't fire as he dies, only when he actually respawns.
Also, this behaviour is not seen in a mission that doesn't use BIS revive.
With the respawn / revive system, player is killed, he becomes !alive very shortly, then alive but incapacitated during revive slot then !alive if this slot expires before player being healed, then alive after respawn.
I guess it's one of the reason BI created the variable "BIS_revive_incapacitated" to check if player is in incapacitated condition.
I agree with you. This alive/not alive shaker is weird for EH behavior.