For the source, Thork/The DMD Developers probably accessed the most recent GIS info for the Country.
I agree that some, like the smooth Compacted / gravel / fine gravel / pebble-stone, Light Green colored roads, you may find get paved eventually, depending on amount and what kind of vehicle use/travel the road department is seeing on it. In my experience, you don’t see the more primitive roads getting upgraded with pavement.
So whatever the GIS info source categorized a road as at the time Thork implemented it, I’d say it’s a pretty good bet that’s what you’re going to see.
The Light Green roads are normally well maintained. Everything else, if anything, they’ll get worse over time, fall to the next lower class road, before they get better.
