As far as I can read and understand the definition, my Model Y with FSD (Not the limited beta release) meets the Standards for Level 3 Autonomy -
Level 3 autonomy means the vehicle can take over all driving functions under certain circumstances. The less-complex highway environment (all vehicles moving in the same direction, no pedestrians, no complex intersections) is the most logical circumstance.
Over 90% of my driving on Rural Roads, 4 Lane Roads and Limited Excess Highways and as an degreed engineer I stand amazed at its ability. I drive 3 days a week 36 miles round trip to my daughters home in a rural county and even on some of the poorest roads with lane markings so faint that I generally cannot see the the vast majority of the time. Yet I can set Autopilot, it stays perfectly in its lane even when being pass by a car in the opposite direction. I have seen numerous Youtube Video (Check out Dirty Tesla) where even in snow covered dirt roads the new Beta FSD is able to drive the car. From what I have seen on numerous new FSD Beta video, it is operating on Level 4.