I'd think it would also be possible to get around congestion problems by using tricks such as multiple channels and/or interference detection on top of BLE. But only Logitech knows how Bolt actually works.
They mean the mouse communicates an absolute position (relative to some arbitrary 0,0 the mouse decides upon) instead of a relative direction.
Dongle can then take latest coord packet and diff it against previous coord packet to get a relative coord to pass via HID to the system.
If the RF packets are lost, some latency occurs but the dongle still has the previous mouse coord and can make a fairly accurate correction once a packet gets thru (get's from A to D, but might skip points B+C).
It could send a "reset 0,0" packet of some form in this case, but now reception of that packet becomes critical to continuing to properly communicate motion to the attached computer.
I am not sure which dongles make these corrections, but my experience with dongles is worse than bluetooth. Typically, a mouse is very close to the bluetooth antenna of a computer, and I have not really experienced any sort of connection issues due to missing packages etc. In contrast, I have had tons of issues with usb dongles due to usb interference.
(psa: none of Chinese ADNS-2610 clones have the raw pixel output debug command. Maybe security implications or maybe something else, either way, mouse-as-microscope hacks don't work on sensors extracted from e-wastes)