Bike brands who say a frame is "perfect" for both sizes loose my respect.Especially for 650B. Hence the question about modern (i.e. being produced now) equivalents.
May I add, that a trend to market a disk-brake "gravel" frameset as both 700c and 650B is, imho, nonsense.
If a bike is built for 650B geometry with 45-48mm tyres, you're unlikely to fit a 700c with anything more than 25-28c into it. If it's built for 700c 48c geometry, swapping them for 650B won't give you the same ride, so it's a very long shot to say that it's a 650B bike.
I cut the disc mounts off of my Sardar, they were fuglyBike brands who say a frame is "perfect" for both sizes loose my respect.
The frame geometry for a bike with a 650x54 fat tyre would be different to 700x28, and the space between the stays or fork blades should relate to the tyre width.
I do feel the same with:
the belt drive stay split and/or eccentric bb with derailleur hanger
- just get the right frame!
Both Canti bosses and disc mounts on a frame are forgivable though - like unused touring or guard bosses.
Dunnois this a show your gravel bike thread or a committee meeting