On Android phones, 1m. Qualcomm chipsets usually have firmware to prevent accuracy better than 3m though.Would be interesting to know how accurate is dual frequency GPS. Can someone post that data? iPhone11 had best accuracy 6 meters.
Your iPhone 11 sounds like it was able to see cell towers (A-GPS) if it had an accuracy of 6m. Using GPS signals only, it would likely be no better than 10 meters.