Dragonkin and reach weapons.

[Egli]

Hello!

I'd like to know why does the Dragonkin using a reach weapons (glaive) only threaten 15ft ?

A large creature with a large reach weapon should threaten 15-20ft right ?

Here's the stats block of the Dragonkin.

http://paizo.com/pathfinderRPG/prd/bestiary5/dragonkin.html#dragonkin

[Java Man]

It is either an error in the statblock, or a special feature of the Dragonkin that is not spelled out in the rules. I would think the first, but could be either I guess.