Phil,
Constantine is also a Warner Brothers HD DVD, not Universal.
Universal HD DVDs do not have any HD DVD promo (other than the brief "Universal HD DVD" Earth opening.
That being said, I noticed that as of the second batch of Warner Brothers' releases, their HD DVD promo is very dark, much more so than the same promo on their first several releases.
I asked about it here and at AVS, but no one seemed to care.
I stopped watching the WB promos anyway, so now it doesn't bother me.

But it does seem weird.
Edit: Ah, Adam beat me to it!