Yeah, but Aerodactyl's not a bird, yet it still learns it. But maybe that's because of the birds-are-related-to-flying-dinos theory...
Also, the Zubat family can learn Brave Bird, but they're not even birds!! Lastly, Groudon and Kyogre can learn the most powerful attacks of their associated types as well as OHKO moves:
Signature moves:
Groudon - Eruption (gets Drought/Sunny Day boost due to Fire-type)
Kyogre - Water Spout (gets Drizzle/Rain Dance boost due to Water-type + STAB )
OHKO moves:
Groudon - Fissure, matches Groudon's Ground-type
Kyogre - Sheer Cold, Ice-type (ice is comprised of water, referecing Kyogre's Water-type)
ThoughRayquaza has Outrage to make up for no OHKO move (it has high power, accuracy, and STAB for Rayquaza despite confusion later), the only move it learns by level-up that references its legends dealing with the sky (Flying-type) is Fly, a moderately weak move compared to Groudon and Kyogre. Several large legendary version mascots can learn 100(+) Pwr moves by level-up:
Lugia - Hydro Pump (references "Guardian of the Sea" title)
Ho-Oh - Sky Attack (references "Guardian of the Skies" title)
Dialga - Roar of Time (references ability to control time)
Palkia - Spacial Rend (references ability to control space)
Giratina - Shadow Force (Shadow Meteor rename FTW, sounds cooler!); references ability to emerge from other dimensions
Rayquaza is currently the only legendary version mascot who does not have a move with the type (Flying-type, in this case) that refers to the legends surrounding it (living in ozone layer, descending from sky, Ziz origins, etc.).
As Aeroblast (with 100 Pwr) is exclusive to Lugia, Sky Attack is the only move with 100+ Pwr that Rayquaza could learn/be tutored (it is not necessarily exclusive to Ho-Oh, since Ho-Oh has Sacred Fire's exclusivity, and several other non-legendary Pokemon can learn Sky Attack)
It just really shocks/annoys me that Rayquaza's type of legends is not represented well in its movepool. Dragon-type does not count since it only serves to represent Rayquaza's draconic image, rather than its role in legends... *sighes*
I just really want Game Freak to rectify this in HG/SS with tutors or tutors of future Pokemon games...
Lugia has Aeroblast
Ho-oh has Sacred Fire
Groudon has Drought
Kyogre has Drizzle
Rayquaza has Air Lock
Dialga has Roar of Time
Palkia has Spacial Rend
Giratina has Shadow Force
The Weather Trio were given exclusive abilities rather than exclusive moves.
Also, Rayquaza always was the odd-ball, as it has Has 2 Types as opposed to one AND a Higher Base Stat Total than Groudon or Kyogre
Rayquaza is more of a Mediator between the two rather than a third counterpart. That's why it's so different in many ways.