I can also confirm this happens.
They just wander off and don't do shit. Doing the "need backup" voice emote doesn't do anything to make them come to you and play the objective.
if you're playing the commander in local play the observers also won't stick with you, even after doing the "need observer" voice emote. This worked totally fine in Day of Infamy and the radioman AI would stick to you more faithfully then any human radioman lol.
I hope they improve local play and not just coop.