Hmm must have missed that I only recall him making a pass at Wynn for knowing her liquor and for getting giddy like a highschool boy if you have a threesome with Isablea and Leliana. But I'll take your word on it, its been a while since I've played Origins since I've switched over to the PC
He makes passes at Wynne, Morrigan, and Leliana. He'll peak in on a female warden sleeping with a female prostitute regardless of the warden's race, and he mentions that one of the things he's learned from his time on the surface is that he's "just the right height to give a human woman a good time".
Now, dwarven girls may well be his favorite, but he wouldn't turn down a human woman if the opportunity arose.
And that's part of my problem with one of the justifications for race gating romances; "people have preferences". Sure, people have preferences. Maybe Cassandra prefers slight elven men to hulking qunari men. That's fine. But someone having preferences doesn't mean that those preferences have to be adamantly set in stone and completely unflexible. Personality goes a long, long way here.