Would the friendly unit on the original card be the only one that could "follow" the moving enemy unit? Or would a unit on an adjacent card already firing at the enemy also be allowed to shift fire? This rule seems to allow the adjacent one to adjust also, but then I see this later:
Only the same-card unit will follow the Enemy as it moves. I'll need to clarify this in the errata.
Example #5 from the Advanced Tutorial (page 11): A lone enemy unit (sniper) moves away but still in LOS… We extend the VOF of the US units in the R2C2 Hedgerow/Bocage into the Sniper’s hex. This is the only case in which a US unit can “follow” a moving enemy unit—when the move extends within range and along the unit’s PDF. So we place an Automatic Weapons VOF on the Sniper’s new card.
This example is representative of "the only case . . . " as described in 6.2.3.