I had a short chat with PB today and took the chance to drop in some of the recent questions. Groups are groups only for moving - they don't affect combat.
Groups are groups only for moving.
Therefore as it starts moving it instantly qualifies as wheeling - and so instantly loses the need for edge to edge contact. So - if there is a pause, or even if an element has moved away, and returned to the group, a group can continue moving as a group from a kinked position. Late arrivals at the flank march. Only the first arrival of the flank march causes troops near the table edge to flee. Stragglers do not count as a flank march arriving.