Per @unknown'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:
/team add TestTeam
/team modify TestTeam friendlyFire false
/team join TestTeam
/summon skeleton ~ ~ ~ {Team:TestTeam}
attack the skeleton
notice how the skeleton takes damage from your attack.
Expected result:
Friendly fire is respected and the player cannot hurt teammate mobs.
I suggest marking this are related to MC-256019 directly as well (and not just via MC-46956), as they're both instances of friendly fire not working for mobs on a team.