1.) I would never let a mapping program choose my routes. I make my own with RWGPS
2.) You can select the type of map you want in the upper right corner so you can cross check if roads actually exist
3.) RWGPS is only about ~50% correct on what roads are gravel vs. paved
This is a tool I have been using for gravel rides. But it does rely on user input for accuracy. I have marked up numerous gravel roads on this map.
https://gravelmap.com/