Ah, I forgot to respond to your first post. Sorry about that.
With respect to bulldogs (and rhodesians), I think there are a few factors at work. First, three-quarters of the collection pictured is pipes by Ingo Garbe. As far as I know, Garbe doesn't carve anything like a bulldog shape. In fact, he works within a fairly restricted range of shapes...I just happen to like them a great deal. For that matter, Joura, one of the others whose work is pictured does not do a lot of work in that shape either, though I do see one on eBay at the moment:
Second, I have only a three bulldogs and related shapes in my collection. The shape is actually very handsome, but it makes me look pugnacious. I already live with the curse of being mistaken for Tony Soprano on a regular basis. :D So, whether or not they were uncommon among German pipe makers, they'd be underrepresented among my pipes.
Finally, I do think that German carvers make less pipes in the shape than, say, British or American pipe makers. Whether they consciously eschew them or not, I cannot say. Although I have no idea of the shape's history, it strikes me as a various British and subsequently American styling. That said, I know that Vauen makes a lot of pipes in the general shape. In fact, one of the more recent iconic pipes by the company is a take on the bulldog:
With respect to canadians, I don't think there is as much of a bias, either way (that is, in my collection or by German pipe makers). There are a fair number of pipes by Garbe that could qualify as canadians (or at least lovat/liverpool/lumberman) if one forgives the slightly brandy-ish shape of his bowls.
Not sure if that helps at all.