Reply To: Pick up and move units
This is the third sentence of rule 7.A. It says units or a stack can “…move into/out of the hex…” which allows them to do things in that hex or head off in a completely different direction, either individually or as a sub-stack of the original stack. It doesn’t say anything about units moving into or joining the stack, or a stack picking units up as it passes through, because that would contradict the previous sentence which says “…units that start a movement or pursuit phase stacked together can be selected and moved as a stack.”
Rule 7.E.3 is about overruns. If you have three divisions each in their own hex and all adjacent to an enemy unit it is likely to be very risky for any one of them to attempt to overrun the enemy unit by itself, but together the odds would greatly improve in their favour. A player might wonder if he could overrun simultaneously from all three hexes or gather all three divisions together in one hex and then perform the overrun. He can’t because:
1) The overrun rule says all overrunning units must enter from a single hex, and
2) Rule 7.A says that units that start the movement or pursuit phase together may move as a stack, and these three divisions did not start the phase stacked together.