Yeah, it seems from moving the cursor that the coordinate display changes corresponding to the area of the map. However, the further zoomed out I am, the more off the coordinates displayed are from the actual world. If I want to get an accurate coordinate set from the world map, I have to zoom all the way in, and even then can be 50-100 meters off from where I am in the world.
When zoomed all the way out, it's wayyyyy off. As an example, I'm currently standing on -340, +250. I hit 'M' for world map and hovered the cursor above my icon. It says I'm at -1150, -242. The numbers change depending on where the map is centered.
Edit - I think I figured out what's going on. In the world map, it's calculating coordinates relative to the top left corner rather than relative to the center. That's why it's more accurate the more zoomed in I am. I just tried zooming all the way in and putting my icon in the top left, and it gave me the correct coordinates when I hovered the cursor over my icon. Does that make sense?
I'm still experiencing this on 1.10.6b for Minecraft 1.16.1, Fabric 0.8.9 build 203, and it makes the world map extremely hard to use. I'm on macOS if that makes a difference. I find it strange that this isn't a more widespread issue. Perhaps it's only affecting macs?