I'll make your point for you by saying my personal experience already disagrees.
I have a 45 F-last suede wingtip that is a perfect fit. I have two Alden Barrie lasted shoes that are 11.0 D and they are both much wider than the F-last. I certainly wouldn't want to go swimming in a Barrie 11.5.
I find the barrie a tad larger than .5 down in the larger sizes (esp shell). but everyone's feet fit slightly differently in dfferent lasts, as the forum wisdom goes of course.