I'm also not a fan of the current implementation (although I understand some people like the idea of RPing all 4 characters at once).
But my understanding is that this is just a placeholder until they implement the "love and hate" feature, which I expect to be designed so that companions roleplay themselves when not controlled by a player.
I will also confirm that I'm uncomfortable with being able to initiate any conversation with any character. The PC should be required to take the lead most of the time. (If you meet an animal, it would be fair for the companion to interject and help out once he sees you trying to talk to a dog. It's much better than having to micromanage and choose the right character for each NPC.)
