Yes, that's the same observation I've done from other parts catalogs. There are many things that can differ enough to make them incompatible, like total length, thread pitch/diameter/length and shape/size where the damper rod passes through, for instance. On the drawing, you can for instance see that there is a spring retainer at the top of the B1 fork, but in the B2 it sits below the spring.
1977 KZ650B1
1980 F1 engine
B1 3-phase alternator
B1 Points ignition
