Using LTE Timing Advance feature, especially on 5G, accuracy can be much higher.

https://5g-tools.com/5g-nr-timing-advance-ta-distance-calcul... shows an example of the parameters necessary. I don't think you can get your smartphone to dump those stats for you, but the granularity of the individual distance measurement is in the tens of centimeters.

Of course this strongly depends on cell infrastructure being placed precisely, continuously updating correction factors, and a bunch of antennae being around the target to get measurements for, but in most cities that isn't much of a challenge if the operator is working together with whoever wants to spy on citizens.