My tests dont show any need for AB BGs to 'form up' before moving off of Allied controlled maps. The BG on Son Heath above should have, within stacking limitations, been able to move to any adjacent map. To quote 17.4.1 in the Manual Addendum:
"There is no restriction on strategic movement from friendly controlled maps, regardless of whether a Battle Group is deployed or not."
However, there should be a restriction on strategic movement from enemy controlled maps even if unoccupied by the enemy. If, for instance, Son Heath had been Axis controlled but unoccupied when Broz's AB BG deployed to an interior VL, that BG should not have been allowed to move on the assumption that it was spending its arrival turn taking control of the rest of the enemy controlled map - in effect, mopping up the nominal enemy garrisons implied by the term "enemy controlled".
As of the .50b patch, the reason neither reinforcing AB BG on Ginkel or Renkum Heaths could move is a combination of 17.2.2 ("On maps that are of mixed control, you may only move along roads for which you hold the victory locations") and 17.4.1 in the Addendum ("Until a Battle Group is deployed it may only exit a contested map (one with an enemy Battle Group present) by returning to the map it came from. If this move is not possible (due to losing the Victory Location corresponding to the map connection) then the Battle Group may not move at all until it deploys."). Since the reinforcing BGs have not yet been 'Deployed' they can only exit the map by returning to the map(s) they "came from". But reinforcing AB BGs come from off-board and deploy on 'interior' non-exit VLs, so there is no map they can exit to.
Two problems encountered in researching the issues in this thread:
1. [Major] - Contrary to 17.9 Reforming and Reinforcements - ("If the Reinforcement Battle Group is trying to arrive on a designated map, but cannot because there was another friendly Battle Group on the map, it finds the closest open “friendly” supply depot to it’s initial deploy map and deploys there.") - the game CTDs if a reinforcing BG cant deploy because of stacking limitations even if there is an adjacent open friendly depot.
2. [Minor] - 17.12.2 MOVE ("By left clicking the Battle Group icon, a yellow border will appear around all adjacent maps. The yellow boarder is thicker for those maps that the Battle Group may move to.") - is bogus information. When you left click a BG a yellow border is only displayed around those maps the BG may move to. And "boarder" ?!? Did the production budget not allow for the use of spell-check?