LOL, maybe there should be a section for the Doctors, and one for the patients. I fail to see how my statement was wrong from a "practical" standpoint. But hey, I have failed with Engineers before and I will fail again. Most of us are on the practical side.
Well, I suppose practically speaking, and Ostwald viscometer uses "flow rate" through a restriction to measure viscosity. Maybe you are ahead of many a layperson here who think that a Brookfield-style viscometer is more commonly used to measure oil viscosity at operating temperature
As far as the confusion with Multi-grade all season oil grade labeling, it certainly can lead to questions and confusion, and then add that most auto parts counter guys and mechanics still use the "It's a 5 weight oil when cold and a 30 weight oil when Hot" explanation, which doesn't necessarily help the average Joe any more. And now we can add rampant internet lore to further confuse .. most anything.
Back to the 1950's.
Many cars recommended a SAE 10W oil for winter use. This was a solvent de-waxed oil with good winter pumpability. We are staring to see 12V systems and starters, so
crank-ability wasn't as important as it once was.
Now, the same car might recommend a SAE 20 or 30 motor oil for temperatures comfortably above freezing - a
summer lube. But, be aware there are differences between an SAE 20 and an SAE 20W lubricant.
At some point in the late 50's Oil Co's started marketing All-Season Multi-Grade motor oils that could be used winter or summer. This is where we are now, ubiquitous among passenger car lubricants.
I hope this journey was a bit fun !
Under-hood oil grade recommendation sticker from a 1955 Ford Fairlane pushrod V8
Vintage Multi-Grade oil Can