I think all exporters do it in some way.
But they all are interested in positive image. So, it is strange to talk "hey, I sell you downgraded version!".
Instead of that you can silently improve "base model" for your own army, while selling "base model" without mentioning that it is "a little outdated".
Not to mention that most selled weapons are outdated by even model.
Also nuclear states have... some kind of immunity against war for their territory.
I think nuclear weapons are the greatest "peacemakers" in human history. I do not even want to think about Europe-Russia-Japan-China relations in world without nuclear bombs. By the strange coincidence there is no great wars in world after invention of nuclear arms. "War for territory" is outdated now.