Here is the real story.
The bike was originally a Hornet 250 in the Japanese domestic market. That bike then morphed into the Hornet 600 with a CBR 600 F3 based motor. That bike morphed into the Hornet 900 (919 in the states) with a 1996 CBR 900RR motor (thats the 9-1-9 one which is the original 893cc 900RR motor with a 1 mm overbore, not the 9-2-9 one, which is a completely different engine) and significantly different head.
The frame is not "slightly different" than a 929, in fact, its not even the same element on the periodic table. The frames have nothing in common other than they are made by Honda & welded together. The 919 is originally based on a 250cc bike.