I haven't seen any official statement on this, but the general opinion seems to be that even with FSD Beta, when the car is on the freeway it is using the same Navigate on Autopilot as a non-Beta car. It certainly switches to the NoAP visualizer. I've seen two different situations though, where the behavior is different now.
First, on my regular work commute there is one cloverleaf freeway interchange that is extremely tight. Previously, when I got near it I would get a message like "Navigation Ends in 500 feet. Unsupported maneuver." It would disengage navigation, I'd take the exit, then reengage on the new freeway. Now, it doesn't disengage, but attempts-* the exit itself. Note that it doesn't switch to Beta mode, at least, the visualizer does not change.
Secondly, now when there is a speed limit change it automatically changes the target speed to the new speed limit. Previously, I'd see it detect the road speed limit, but would have to change the target speed myself. I confirmed that this morning while I have a loaner M3 while Service has mine. It behaves as I remember mine doing pre-Beta: the speed change must be done by the driver.
* - I put "attempts" because I always have to prevent it from finishing the merge. The cloverleaf ends at a merge lane that lets you get back to speed then join traffic. It always tries to clip the apex of the entrance, skipping the merge lane, and driving straight into the traffic lane, seeming oblivious to the traffic about to mow over it. This is always during the morning commute. If I'm ever headed that way when there isn't a boatload of oncoming traffic I'll let it finish it's maneuver and see just what it does.