Not sure if this is intended, but seems more likely a bug. Using the console command or calling it in a script has no effect. Seems to work fine in hard mode, but in normal mode it does nothing. Since actors set to player teammate are automatically set to essential there is no way to set them back to non-essential (in normal mode...) other than removing them as a teammate. I'm curious if this was present in the earlier versions, before the last patch that fixed an issue with random essential actors in the wasteland, or if it was introduced with that patch.

In any event Devs please fix this, I see no reason why this function should be disabled in normal mode.