Although technically it shares very similar aspects to the bow saw it's intended use is rather different. This is aimed at a replacement for the tenon saw, hence the depth of the blade and it's inability to turn corners. I understand these types of saws were much more common on the continent.
I suspect it's a little unwieldy for cutting fine dovetail joints but I guess there's no reason why a smaller version (with very fine teeth to the blade) can't be made. I don't think Sellers states where he got that blade from. The Japanese blade from Fine Tools is mighty good but will need cutting down to length. It also gives a kerf of just over 1 mm iirc, which might be a little on the large side. I suppose the other option is to use one of the blades intended for the guided mitre saws, although the one such blade that I bought from Axminster didn't give a great cut. Maybe the original Nobex types are better.