I first began using Grindr in 2012 at which time the App was Geospatial with accuracy near read as the standard unit of measurement United States. Is your phone on Roam? The Mile and Feet programs must be defunct or it was decided that these programs offered no real profit.
I frequently encounter Distance irregularities much the same as you which, in a location basesd service, I would expect to be accurate within an outcomes based explanation.