In my experience, my Iphone 11 is quite often wrong up to 20-30 meters, depending on nearby buildings or other environmental factors. Other phones at the same location at the same time can also differ the same distance, but not necessarily in the same direction.
Depending on the use case, within 50 meters of each other may or may not be considered ”the same location”.
Magnetometers don't use GPS and IME can even be thrown off based on their proximity to metal objects. Things like multipath also won't impact all devices equally if they're adjacent
Depending on the use case, within 50 meters of each other may or may not be considered ”the same location”.