[17.5 End of mission screen] Dead soldiers come back to life?

Smoke grenade is possible trigger, I threw one, it landed at a soldiers feet (instead of the spot I wanted) soldier made death sound during hidden movement leaving just his medipac on the ground, later, aliens shot and killed a second soldier and wounded a third in area smoke grenade used to cover.

at end of mission the two dead soldiers needed 4 days in the hospital to recover, the heavy wounded survivor needed 17 days in the hospital

Soldiers (and aliens) incur stun damage if they stand in smoke, your first soldier probably just fell unconscious.

There is a mechanic that allows dead soldiers to be revived. Depending on how much "negative health" the dead soldier has (a soldier with 60 HP that takes 61 damage has a decent chance, at -20 HP there is 0% chance), he may be revived at the end of the mission with 1% health, spending 17 days in hospital

ummm but both of my "killed troopers" showed up needing 4 days to heal, the guy who has 10 health and finished the mission needed 17 days 0.0