So I get why they would have wanted to eliminate starter movement to get there in one hop from Lorien.Wizard companies cannot use starter movement to or from sites in Gorgoroth. If using region movement to or from sites in Gorgoroth, they must move from a site in Imlad Morgul, through either Nurn or Udûn, or use a movement enhancer like Ash Mountains or Eagle-mounts. Such sites may be reached normally with Under-deeps movement.
What I don't understand is what the restrictions on region movement are designed to prevent.
Imlad Morgul, Nurn and Udun are the only adjacent regions to Gorgoroth. I have to come "from a site in" Imlad Morgul if I want to go that way, so that would necessitate a stop at a potentially dangerous site, but it says I can just opt to move "through" either Nurn or Udun so it seems like the easiest way is still the backdoor Horse Plains -> Nurn -> Gorgoroth.
And the rule further goes on to say that I can still use a movement enhancing card or Under-deeps movement.
So what is this rule trying to prevent? All I can figure out that it does is make it undesirable to thematically pass through Minas Morgul/Cirith Ungol on the way to Mount Doom.