Well we discover something, you don't know as much as you know about motorcycle history (I'm no expert but don Antonio I know
Antonio "JJ" Cobas was the developer of the "Peripheral" frame, before him the great mayority of motorcycles frames where "Spine" (with a thick tube on top that hold the head tube and in the great majority a "Cradle" that holds the motor from the bottom..
this is Don Paco Bulto the owner of Bultaco, I show you a "Dirt bike" to make the difference more obvious, before Cobas the GP frames where closer to the Bultaco, main spine with some gussets, very few use the motor as a stress member of the chassis (Like John Britten did, but was not his invention)
the perimeter "delta" frames have a massive advantage in torsional stiffness, including very rigid/stable forks, so much of a advantage the four big ones had to contact Cobas to make them frames base on his concept, if not there where not competitive and you know how Japanese are with pride... i think the year was 1971 or so...