Mystery MAC addresses in bluetooth

This is a screen recording of the available mystery bluetooth devices in a bus. There were between 5-9 people at the time. I saw 16 devices. You will also see the distances to the device from where I was. This was using a bluetooth tracer app. Then I switched to the built-in bluetooth finder in the settings. In there I only saw the two bluetooth devices which were in the bus - 13/VAL-TX... Why is that? Why are there mystery MAC Addresses. No device name and no vendor. If I do an online check on these MACs, they aren't assigned to any vendor. Does anyone have an explanation? The OS version was Android 11. If you were to use an earlier version of Android, you will also see these mystery MACs in the built-in bluetooth scanner. I have done more testing and with other bluetooth apps and they give similar results.