OK, I'm game, more comments for an old thread. Was it about 1973 the DOT mandated the uniform shifting on the left, & right for rear brake?
As to 'rotary shifting,' pretty sure that Bridgestone was one of the manufacturers doing that. Bridgestone was distributed in the USA by Rockford, and enjoyed a lucrative % of the motorcycle market here. They had a reputation for engineering innovation. Some of the things I recall from back then were rotary valves on two-strokes, and an emphasis on performance, easy and relatively inexpensive to achieve on two-strokes. their singles and twins were well-received in the marketplace, and while the styling was definitely Japanese, it seemed to be a bit more-appealing than some of the other manufacturers. The couple of bikes I recall being excited about from Bridgestone were the 175 Hurricane twin, and he 350 GTO. Both had better than normal levels of performance. The bikes had good ads too, and since word-of-mouth was positive, they were successful in the USA market. The 350 GTO was capable of being tuned to British 500/650 beating levels of performance, and racetracks saw the 350 GTO earn its 'giant-killer' reputation. For those on a budget, the 175 twin two-stroke was capable of class-leading performance.
You might compare the Bridgestone to the Kawasaki of 1969+. Performance oriented, affordable, and word of mouth was good. So why isn't Bridgestone in the motorcycle marketplace now? Two words: Honda threats.
Honda was already the #1 manufacturer, a title held by BSA in the 1920's, and then DKW after WWII (they developed the resonant expansion chamber for two strokes, boosting power tremendously and they had the largest engineering staff in the industry, they had more engineers than some of the English companies had employees!) but upstart Bridgestone was in possession of a small but lucrative part of the motorcycle industry. Bridgestone also manufactured motorcycle tires, and they were an OEM supplier to Honda. Honda gave Bridgestone a choice: "sell us motorcycle tires, lots of motorcycle tires, or sell your own motorcycles, and no bike tires to us!" Bridgestone made their choice.