From mrpingouin1's comment on MC-89773:

Can confirm for all non EntityLiving entities.

AreaEffectClouds do not respect teams when using an @e selector.

Problem:
– Type the following commands into command blocks and run them.

summon AreaEffectCloud ~ ~1 ~ {CustomName:"BrushTest",CustomNameVisible:1,Tags:["BrushTest"],Duration:6000}

scoreboard teams add Red

scoreboard teams option Red color red

/scoreboard teams join Red @e[name=BrushTest]

execute @e[type=AreaEffectCloud,team=Red] ~ ~ ~ say Something Should Happen

— result —
The AEC's name will turn red, and show up on teams list. But it won't execute the commands.

— Desired Result: —
[BrushTest] Something Should Happen

Other entities work with the team selector filter, but not AreaEffectClouds!

Remove the "team=" filter, and every AEC on the map executes the command.