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.)
What if you think of it as the PC telling party member 3 "hey, you're a dwarf, they're dwarves, maybe you should talk to them instead of me"? :p
The thing is, they want the game to react to different characters in different ways, and if the player can only do a given interaction with their main character, then that severely limits how much content they see per playthrough. Replayability is great, but the percentage of players who will play through any game more than once is tiny. And with five races and hopefully at least two origin stories per race, there's still room for lots of replayability even if you can see the unique stuff for each of your four party characters.
