Sorry, Bronies. So far from what I've read, he never actually does the deed with the Centaur girl. In the novel, he talks about how he just doesn't find the lower horse half attractive lol.
There is a point where Gruwald DOES mistake MCs good intention as a sexual invitation but he shoots it down real quick. Then it leads to one of the best parts of the story, when the dwarf (who is seriously the real MVP of this story) has to break it down for the main cast about this whole village mentality of treating the chief like a baby maker isn't healthy. 😝