That's my thought exactly: there's no logical reason for this to need to send your location, so it's probably monetized by AMap to improve location accuracy. The fact that it's not disclosed is worrisome but sounds more like incompetence or ignorance to me.
I haven't taken the time to fully dig into your posts, did you notice if they're generating a user ID? For me, that would be the difference between using it for location accuracy or tracking user locations. That being said, the data they already have is probably more than enough to track individuals.
Reminds me of this one post that I just can't find anymore: a (danish? finnish?) journal bought a pack of "anonymized" location data and chose one individual. They were able to track where they lived and worked, and where they went for vacation. They even went to their place and talked to them, and they had no idea this was happening whatsoever. I really wish I could remember where I read it.