I agree it follows previous experience that only the top form would be used. I think druids feel it more though because there are so few skills / spells that can be used in combination with shifting. I don't know all the details, but for example there could have been:
Natural Fighting - druid skill - enhances combat abilities for some attacks that consist of a claw/claw/bite routine when the skill check is successful.
Tail Slap - druid skill - Druid learns to use a tail when shifting to forms that have a tail pinned on them. Tail slap does some minor combat damange, command acts like a kick. Larger forms may be able to knock targets off balance. Largest forms may be able to hit multiple targets.
Breathe Specialty - druid skill - Even dragons aren't born with perfect skill at breath weapons. This practice allows a creature to get the most benefit from breathing elements at her targets. (reduced save chance? reduced mana cost? only applies on successful skill roll)
etc etc, gotta get back to work