That is how locations are transmitted for Find My Phone/Device, and how relative close-by positioning works for AirTags and similar, but it's not used to determine absolute locations as far as I know. It would certainly be cool if it did that though.

You might be thinking of https://en.wikipedia.org/wiki/Differential_GPS.

3GPP Release 16 started the UWB location and position scope while Release 17 finalized the 5GC capability. Perhaps more work is being done there, I haven't been tracking it closely lately.

https://www.3gpp.org/technologies/location-and-positioning