That used to be the case, but was changed a few patches back.
as far as i know, paradox denied that the 'rule' was even there.
can anyone give a source for the 'ai can take long way around so they can take shortcut" got fixed?
I still see it happen alot; ai just coming in from south on occupied fort, only to leave occupied fort north side..
then people will say "it's due to something else"
no matter what 'rule' allows this, its just a mess of a ZoC if it is allowed.
good example would be samarkand and fort south of it. ai walks from south on occupied fort, and then can attack you in samarkand and just bypass your occupied fort...