It's 100% on the more efficient rear permanent magnet motor unless more power is requested or slippage is detected. I don't follow this topic super closely since I don't live in a region with snow/ice, but I recall a Bjorn video from a while back saying there was something of a snow/ice mode in more recent firmware. Nothing user selectable, but when traction was limited in slippery conditions the car would default to something like a 50/50 split for some undetermined amount of time.
Edit - after seeing
@coleAK response above, I'm wondering if you've felt any difference in the last year or so? I'll see if I can find the video and firmware version. I recall him saying he basically had to floor it to force tires to slip before it would go into the balanced torque split. Your description fits everything I'd ever heard up until that video I mentioned though (rear breaks loose, front kicks in to straighten out, cross fingers and hope traction control doesn't screw up).