When you say "GPS coordinate tracker feature", do you mean the actual GPS coordinate numbers? Maps.me is popular not just for offline maps but also it's ability to load kml overlay. They are many sources around the internet and once you email yourself the kml overlay attachment the Maps.me app will load it automatically. It's nice to see the route line and know straight away if you are off the route. As for the coordinates I don't see any need to really use it as long as you know where you are on the Map in respect to the route (added feature of the kml overlay).
As for GPS, the good thing about mobile phones is that most of the time they find your location via triangulating from the cell signal, not the GPS satellites. You not only get your location even while indoors, but almost immediately, GPS only will usually need 20 seconds or more.
For me, only one device (phone) to carry for all my caminos with Maps.me and route overlay. An overkill for well marked popular routes like
Camino Frances or Camino Portuguese but for less trodden routes like certain parts of Camino Mozarabe etc. it saves me from getting lost and helps me figure out other alternative path numerous times. Sometimes you see a road that is much shorter than the path and you realized why you are on the path (safety). So after a while walking on the path I decided to cut into the road only at the last km to save 2 extra km of walking on the path. A bit of juggling between risk and distance, something you have in your hands with these tools but could be something that is too much of a distraction and for some pilgrims. To each their own....