No, "the distance light travelled" is not even well defined, let alone a primary concept.OK, first "the distance light travelled" is the most primary concept in SR. The distance light traveled is the primary logic used for clock synchronization and LT is based on that.
Clock synchronization is based on a distance defined by a ruler, and the time taken for light to traverse that distance. The ruler defines the distance, not the light.
I really don't follow why you seem to think that special realtivity relies on the poorly defined concept of "the distance light travelled".