It doesn't bother me that the head tube and steer tube are not db 531. These are 2 tubes that you don't want any flex at all. I've had and have alot of 531 forks and never seen a seam, in the steerer. Never bothered to look in the head tube! I do have an all 531db TREK bike that has a Tange fork from the factory. The Yellow Jersey in Madison, who used to be a top Trek Dealer said that was normal.
Dickey Greer
West Monroe,LA USA