Update: recently found the surface=paving_stones part of the track. It began with three branching similar short tracks, two of paving_stones surface and one with small gravel-like surface (at first glance).

Following the traced paving_stones branch brought me to a closed (likely private) high gate, with no marked traces whatsoever of the surface=dirt portion: it was not a marked path anymore. Even worse, rechecking from the uphill end node of the surface=dirt path intersecting the highway=unclassified tagged road there were no signs of any marked surface=dirt paths either. I’ve noticed even some one meter of slope to get to the (off-track) ground.

All this sounds like someone traced up a non-existing short dirt path by jumping the track and shortly making way in the woods.
I think this shortening connection will get cutoff one day.