OK..., where's the popcorn emoji?
The following is what we've learned & come to believe over some decades of curiosity & reading hard copy articles & studies, beginning pre-intewweb, such as Kevin Cameron's excellent series on motor oil during the heyday of Cycle World, and various later publications found on oil manufacturers' and enthusiasts websites. Your beliefs will likely vary.
The vid doesn't address at all the environment of motorcycle crankcases that share oil with a constant-mesh transmission, only that of the relatively benign working environment of a car motor. As far as it goes, it's an interesting vid. Much has been written about the differences car motor vs motorcycle oil operating environment, and is beyond the scope of what we're about to write.
As mentioned, motorcycle trannys shear oil molecules in ways that car motors don't. The shearing action of the tranny gears directly & negatively affects viscosity over the life of oil in a shared-crank/tranny environment in a relatively short time. There is a case to be made that synthetic oils fare better than dino oils when subjected to the shearing action in a shared crankcase/tranny environment.
Air cooled motors subject oil to higher temps than liquid-cooled motors. Heat accelerates oil degradation. Air-cooled motors should have oil appropriate for their unique needs.
The vid only briefly touches on oil age, as in "exposure to air". What that means is, oil oxidizes when exposed to atmosphere. That's a deciding factor in changing oil due to time vs. mileage (or operating hours).
Oil must achieve a temp above the boiling point of water (~212 deg. F, or ~100 deg. C.) for some minimum time to help evaporate blow-by contaminates (mostly H₂O) collected during cold starts & warmup running. One of the most damaging contaminates is the sulphur dioxide (SO₂) that is a byproduct of combustion. Another byproduct is water vapor. Combined, SO₂ plus water vapor creates a weak sulfuric acid solution that ends up in the oil. Evaporating the water mitigates the damage that can be caused by allowing the dilute acid to remain in the crankcase. Frequent oil changes drains remaining contaminants.
There has been some ancedotal evidence that synthetic oils can 'weep' past gaskets that were oil tight with mineral oils. We'll leave it at that.
Even purported dino oils' additive packages are likely at least in part synthetic.
JASAO MA-rated oil is strongly suggested for wet clutches. "Energy-conserving" oils are not.
Further reading:
motorcycleinfo.calsci.com/Oil.html
'Nuff said. There's more, but consider this our most basic contribution to ongoing the popcorn feast.
Not to leave well enough alone, there's also the subject of oil filters: A whole 'nuther can of worms.**
Somewhat dated, but covers most of our stuff, which is dated anyway:
motorcycleinfo.calsci.com/FilterStudy.html
and
motorcycleinfo.calsci.com/FilterXRef.html
Done for now. Gotta go to the store & pick up a case of popcorn.
** Zymurgy's Law of Evolving Systems Dynamics: "If one opens a can of worms, the only way to re-can them is to use a larger can."
Good Ridin'
slmjim & Z1BEBE