Originally Posted by
WhyFi
They do account for/make assumptions about rolling resistance with regard to bike type - indicating an MTB will get you a higher power estimate than indicating a cross bike, which will be higher than a road bike, etc. They also do have surface type info available on their route creator, though it's not comprehensive, so they could, in theory, add that as a factor in the future. That might be a lot of work to do for what'll still be a crappy estimate, though.
All gravel not being equal, it really would be just one more piece of GI/GO.
My basic thought on this is that if you want to be able to make comparisons between people's power outputs, you've picked the wrong activity.