ORIGINAL: Nikolaj
Thanks for the help. Yes, according to the supply mode, they should be isolated. Here's the picture you asked for. This is from the autosave, at the start of the turn:
Looks isolated ok. As PeeDeeAitch said those units that can relocate out of sealed pockets are HQ and Air Bases. It works as intended this simulate the fact that in many cases Generals and high staff were evacuated from pockets with planes when pocket was about to collapse. There is high risk General getting killed if HQ is forced to relocate out from pocket. I have lost my best general some times this way.
This happened in World War 2 for example when Africa Corps was sealed in North Africa Luftwaffe saved Rommel and his HQ and also People were saved from Stalingrad pockets by Luftwaffe.
Planes can always fly out from pocket with relocate but they have to leave damaged planes behind and also bases take some extra attrition. This simulates air force capacity to emergency air lift itself out from pockets.
No other unit can flee just HQ’s and Air bases.