Open a scenario or spawn in editor.
Press M.
Zoom out.
Watch the map get textured grid by grid.

Alternatively launch Arma 3.
Open editor.
Press textures button (Crt+T).
Watch the map get textured grid by grid.

I'm not aware of the limitations or the demands of the map by I imagine that it cannot be that high to load an interactive map with some squiggly lines on it so a fix for this would be nice. I don't ever recall Chernarus or Takistan doing this even though they were slightly smaller so I imagine it is a bug/optimization issue. If this has already been address I apologize, I searched both map and map render/load but did not find a similar issue.

This also happens in the editor on first load when you click the textured option.

Attached is an image of the map filling itself in on the bootsy's popular mission Morning Wipeout (hosted as a SP scenario).

i7-3630qm
Nvidia GTX 670mx (Driver verson 327.23)