OK, that makes a lot more sense now. One other thing I do see is someone abusing this rule to get an extra move for some of their units–if I owned a territory that was inaccessible from the territory my army was in, but my enemy owned a territory (with a factory in it) that bordered both of my territories, I could launch a strategic assault against my enemy’s factory and then “retreat” my forces into the inaccessible territory.
For example, a German army could launch a strategic assault against Karelia S.S.R with the sole objective of moving an army from the Baltic States to Finland, or launch a strategic assault from the Eastern Ukraine into Russia, and then “retreat” their forces into the Urals or Novosibirsk once the first round of combat was done (assuming the Urals or Novosibirsk were controlled by an axis power). In each instance, the assaulting nation could attack with a force much too small to actually take the territory, yet still get the advantage of moving through the territory as though they had actually conquered it.
I like the idea of strategic assaults, but if I was going to play a game with them I would require all assaulting land units to retreat back into the territory they had originated in once the assault was over.