Perhaps, perhaps not. No-man's land provides a quick-fix to what is a deeper problem that you mention in the other part of your post. Sure, in Africa/Asia it renders the game quite literally unplayable in SP, but it has ramifications even with the NML switched on as the AI doesn't seem to understand supply (and quite frankly, a lot of other variables that any half-competent human player like me will take into account while deploying his armies or moving them around). Of course, the easiest thing the developpers can do is put in un-passable terrain. Or, they can work at the AI to ensure that without any terrain being 'impassable', it takes into account supply, attrition, etc and therefore simply decides not to venture into Sahara/Himalayas.
I think/hope that developers are looking to perfect the second solution, which will ensure a better AI overall instead of a quick fix.