In the entry for dragons, immunities are mentioned as follows:
Immunities (Ex): Every dragon is immune to sleep and paralysis. In addition, a dragon is immune to one or two additional forms of attack no matter what its age, as given in its description.
In the entry for Imperial Sovereign Dragons, they are listed as only having the two base immunities, sleep and paralysis. For example, the adult sovereign dragon:
DR 5/magic; Immune paralysis, sleep; SR 26
Is this deliberate, or have they accidentally been short changed?