Scoreboard teams add "@e" doesn't work correctly
First of all, I am not sure if this is really intended
Perform this command:
/scoreboard teams add @e[type=Player]
It will give you the output that the name is too long, so it isn't using the actual player name (it is using the UUID), but it should be the player name as all other commands with @e[type=Player] use the name and not the UUID