Question why does my frame rate get halved in the editor when I have a second active game tab open?

Basically title. In the editor, if I am trying to use two cameras and display both of them in separate game tabs/windows during play mode, I noticed that my frame rate is halved. I have capped my playback frame rate at 60fps, this is much lower than the maximum frame rate I can run the game at in editor, so it is not a question of demand on my gpu/cpu.

Thanks

 

I would also be interested in knowing if this is a problem specific to me/one of my scripts, or if this is something everyone experiences with the Unity editor