Brooks do to some extent.

They've always recommended the different models as suitable (primarily) for different positions. That's not to say you can't use a Swift with a high bar position or a B17 with a low one but they are designed differently on purpose and for intentionally different riding positions. I think however that over time some of it has been 'misrepresented in repetition' in that B17 is not exclusively for 'upright' riding as such but for 'less extreme' angled/racing riding postion.

Brief and simplified* version is:

B17 for minimum bar drop/bars level (or above saddle)
Team Pro/B17 Narrow for small/medium drop
Swift for medium/high drop
Swallow (also) for medium/high drop.

Over the years Brooks have explained this either by vague terms like 'more upright' and 'more aggressive', and by quoting riding position angles (like they do now ie: 45deg/60/90), so although they've always been differentiated by intended riding position it's not always been exactly clear what they mean by that, and it's even more vague when you also have width playing a part. There's a lot of overlap in what can work in what position but they are definitely intended for different riding positions not just different sit bone widths.

There's more to the differences in shape that meets the eye on first glance. Not just width across the back of the cantle plate, but in flatness and angle of dropoff at the sides of the cantle, and also differences in absolute nose width, where and how quickly the nose tapers and how flat the saddles are fore and aft.

*And the B67 and flyers for properly upright town bike position.