Shift feel deteriorates with some oils, and fairly predictably, period. Ride enough bikes and different oils and it's evident. Right foot shift, good save on that one as legislation was passed in the mid 70's that made BSA move it to the left. Most folks here would not use that as the basis for a comparison as it's been 50 years more or less since the last right shift bikes were sold in this country, and dang few of them at that. I'm sure that was a test to see if folks were paying attention. Humor intended.
BLS, I was making the observation that saying oil cannot shear two grades, is absolute. There is nothing to my knowledge saying it cannot shear two grades, only that in most analysis it is down one grade as you have shown. Apologies for not being clear on that. Sounds like Jim at Mobil doesn't ride much, and would never say anything about shear if he wants to keep his job. Good CYA answer from him.