Hi @jenebean. Thanks for the question. You do have the "copy from sub-season" option 2 different ways: copying sub-season within the same Season AND "copy from sub-season" when creating a brand new Season. I'll review both options.
New Season
If you are creating a new season and choosing "copy from sub-season," if you delete a team, it deletes it from the new season only. If you edit a team, this will also edit the team name in the existing season as well.
Within The Same Season
If you are choosing to copy a sub-season within the existing season, if you delete a team, it will delete if from all sub-seasons in that particular Season. If you edit a team, this will also edit the team name in all sub-seasons within the Season as well.
Bottom line, editing a team will cause the edit across all team instances.
Hopefully this helps! Please let me know if any questions.
Jessica