Probably depends on the stage of the relationship.
At the very beginning, I expect to be very much focused on each other, and checking others out constantly could get annoying. Once a relationship is established, though, that's more of a bonding thing, and although I'm straight I could be the one pointing out a woman to him.
Ultimately I wouldn't make a rule out of it, I would only call someone out on it if they do it the whole time and I feel like they're not listening to me. I'd feel like I'm boring them. Doing it only a couple of times during a date would be fine, I think.