Per Moesh's comment on MC-46956, I'm making a new report for this.

Players can hurt mobs on the same team, unlike other players, when friendly fire is false

Steps to reproduce:

1. /team add TestTeam
2. /team modify TestTeam friendlyFire false
3. /team join TestTeam
4. /summon skeleton ~ ~ ~ {Team:TestTeam}
5. attack the skeleton
6. notice how the skeleton takes damage from your attack.

Expected result:
Friendly fire is respected and the player cannot hurt teammate mobs.