I don’t know about the Marines but I spent my first 18 years in the Army training for woodland combat. Everything was geared towards scrapping in the woods until OIF came along. Desert fighting is easy and woodland training more than suffices to make the transition. Now Urban and mountain warfare is a different story all together. But we are all getting a graduate level education in both.
Its just a matter of time before all those patterns get mixed and matched. Every Russian soldier I saw in Bosnia (98) had different tops and bottoms. I cant recall any of them having a complete matching uniform.