i never use cycles models and sketchfab so I dont have loads of personal experience with this , I can however recall several posts where users who have uploaded cycles models have had material issues , many post such as these… This leads me to the conclusion that cycles is simply not supported much for uploading to sketchfab.
While it would be great to not have to do any manual material settings , such a thought is a pipe dream , even if there was considerable work done in this aspect , it would still never match cycles to sketchfab perfectly as blender cycles is an offline renderer and sketchfab is a realtime renderer. There are many features of cycles that do not have an equivalent in sketchfab. For example uv scaling as you mentioned , this can be done via nodes in cycles but there is no such feature in sketchfab , if you want tiled UV , you need to scale the actual uv islands above the 0-1 range in blender manually so the desired tiling works in sketchfab. Also cycles can do many variations of procedural UV mapping , which i think when exported will have no UV map information… just an example. There was extensive work done by somebody on the new sketchfab to blender model importer … perhaps they should be the right person to look into getting better support of exporting. As mentioned it will never be full support and you will have to tweak things but a better base export import can save some time
I cant view the model as it is not published and im not staff but from the description James mentioned it does not even sound like many items. To be honest in this profession doing material settings per platform is kind of always expected for superior results as automation normally is not clever enough to give the best results compared to doing it yourself. Just set it up manually , 20 minutes and you are sorted