I could overlook it as an error, except they have sample dragons at every variety and age category in that book, so there's already an Adult and Young Adult Blue in the same chapter as he is. I limited my brief scan for banality to the older ones (Mature Adult+) for precisely the reason you described.

I just find D&D dragons to be on average as boring and childish and disappointing as D&D deities, for precisely the same reasons. With great power comes great ennui it seems.