Tagging a tile can be used to see the exact tile type
If you tag a tile next to already revealed, you can reliably see whether it has any gold seams, or can be dug. The blue "tagged" texture will show up fully through FoW.
Game Version:
Steam Public
Platform:
Windows
In tests I found this to be correct. The new "atmospheric" fog of war extends slightly in from the edges of the real fog of war. This means the fog will look like it extends farther than it does and is intentional.
Essentially you can really see two tiles beyond any of your walls, but objects will appear obscured, tagging them will reveal them in the same way that hovering them with your mouse does or viewing the minimap. Anything beyond those tiles is considered "Fog of war" and does not display anything but dirt when tagged.