There was a bug that would allow a tamer to get higher stats when taming a pet, through the use of buff spells during the taming process. It has been fixed for some time now. I cannot recall the exact publish. This same bug could also make the pet have lower stats. I was unfortunate to have an excellent greater dragon only be able to achieve 119 Stamina, when it was at 125 Dex, which really hurt its swing speed (0.25s faster per 30 Stamina), due to this bug.
The hiryu above was likely tamed under those effects, since it has a greater than maximum stamina and its stamina and dex values are not equal, in addition to having greater than maximum hit points. The hiryu's stat range has not been altered by the developers.
Stayin Alive,
BG