That looks normal for basic Autopilot and EAP. FSD beta gives you visualizations of all or most of the cars it sees. The cars that don't show up in AP are still seen by the car and are taken into account for driving and safety if needed (in which case they would probably show up). Only the visualization is missing.
There are thousands of FSDb videos on YouTube. If you haven't done so already, you can take a look at some of them to see the large number of cars that are visualized.
The situation is similar to traffic congestion visualization and premium connectivity. To have congested areas show up on the map, you need to pay for premium connectivity. But the congestion is still taken into account when routing even if you only have the basic free connectivity.