When placing a hostile mob into a team with the player, usually they are non-hostile to the player from that point until they are no longer in the team with them.

When I attempted to do this recently I still got attacked by the mobs I was in the team with, the command block outputs even confirmed they were in the team, as was I.

I created the team Skeleton

I created an always active repeating command block to add any entity with the type minecraft:skeleton to the team skeleton

Then created an always active repeating command block to add players with a certain tag to the team skeleton

I expected the skeletons I encountered to be non-hostile upon entering survival mode, as I have done many times across different versions, but was killed shortly thereafter.

Thank you for your time and effort.