In JOSM you can turn on a tms-layer that shows gps-traces from OpenStreetMap (tms[20]:https://gps-{switch:a,b,c}.tile.openstreetmap.org/lines/{zoom}/{x}/{y}.png). I did that, being happy that there is an option to show relatively easy uploaded gps-traces. After some time I realised me that are much less traces shown then when I download them directly from the OSM-server.
So my question is, why there are differences between this tile-layer and the downloaded gps-traces? Maybe these tiles have not been refreshed since a long time?
Your assumtion soundls quite good, but I don’t know the reason exactly.
Maybe you can ask this issue at http://help.openstreetmap.org … there are some of the core developer guys present, at least more than in this sub forum.