I believe that fender specs must refer to the internal width, but I've only actually measured the one. I've dented fenders before to get them to fit a fork, but I don't like leaving them with the sides contacting the frame, going further would probably reduce the tire clearance too much, and that messes up the fender line. Since forcing a fit is kludgey I'm just going to wait and buy some of the Berthoud fenders when there's room in my budget.
I was hoping they'd leave the hanger on that size and should have sized up instead of down to be on the safe side. I don't know why I didn't attempt to verify with an email, because I've never been very happy with losing that feature while paying the same price. At least in this case there's a substitute instead of expecting people to buy a seat bolt hanger. I'm not thrilled with any of those. Whatever is taking priority when frame designers drop the hanger I wonder if I'd rather have a hanger with a useful barrel adjuster instead.