The bug

When you set a scoreboard to display for a certain team color sidebar.team.<color> it doesn't show that objective to the players with that team color. (It still only shows the objective in the sidebar slot)

How to reproduce

1. Add an objective:

   /scoreboard objectives add obj dummy
   

2. Set the display

   /scoreboard objectives setdisplay sidebar.team.blue obj
   

3. Add a team and set its color

   /team add blue
   /team option blue color blue
   

4. Set your score for the objective

   /scoreboard players set @s obj 256
   

5. Join the team

   /team join blue
   

   --> As you can see, nothing displays on the sidebar