This is also my post.
I try this approach on my PC with better graphic card and GPU. (i7 8700, RAM 16, GTX 1070ti)
The problem is still the same as on surface pro, the texture size setting cannot set above 2 (large).
When I start the game, the texture size always change to 2 (even I set at 3 in general.opt).
At large texture size (2), I think region 4625 cannot be render so it appear as orange block.
(Like when we set it below that, more region will appear like that too, include some sea zone.)
So I think if I can set the texture size to very large that may solve the problem.
(In EAW I can set the texutre size to 3 via general.opt, all look fine
and the plain color region in Africa, Spain and Scandinavia is intentional.)