For me, the guy his method is fairly simple.
He has access to the equipment to perform a selection of tests that provide consistent results so an "apple to apple" comparison can be made between different brands and types of oil.
The "Load carrying capacity/film strength" provided for each test indicates how much force in PSI is required to shear the oil film, and at that point metal-to-metal contact will occur.
It does not matter at all if you want to relate this to a flat tappet lifter, piston ring or connecting rod bearing, the theory remains same of simple math between Force (pounds) and Area (sq. inch) and does not require any form of API or ASTM standardization.
These standarizations are guidelines based on certain specifics, if you made modifications to your engine you can be already outside those specs and any API or ASTM standard means nothing.
(as example, you running bigger/smaller bearing clearances, higher valve spring pressures, drilled out oil channels with bigger oil pump, etc are things that alter the minimum requirements compared to the stock engine the API or ASTM spec was provided for.)
As an example, you want to use an oil that has a film strength of 80,000 psi and you wonder if this will protect your cam and lifters.
As example, the actual contact area between the cam and tappet is 0.01 sq. inch and you are using valve springs with 600 lbs spring pressure at full lift.
80,000 psi x 0.01 sq.inch = 800 lbs
This means you can apply 800 lbs of force on that area between cam and lifter before the oil film loses the capability to prevent metal to metal contact.
The allowable load of 800lbs is higher than the load caused by the valve spring (600lbs) so the oil film will remain intact.
In that same example but using an oil with only 50,000 psi film strength, you see the force is only 500 lbs, there will be metal to metal contact as this oil is unable to provide sufficient film strength against the valve spring pressure of 600 lbs.
Don't consider the 50,000 psi oil in above example as bad, it just does not suit the above application.
That oil would do just fine on a stock rebuild engine with 300 lbs valve spring pressure.
But this is purely based on the valve spring pressure example, if that same engine has a high compression with high cylinder pressures it still might not be sufficient for your connecting rod bearings.
Yes, that is hard to judge as not every load can be calculated as easy.
This calculation can be done on any engine part that is protected by an oil film, if you know the Force and Area.
A main or connecting rod bearing, drive gears or a piston ring will be covered in the same manner as above example.
Though it is not really as simple as above as there are more forces involved, resistance/friction factors and variables as temperature, oil life/condition, oil contamination (solid particles/water/fuel) that will have an effect on it all.
But it is obvious that the higher the number (film strength) the higher the level of protection is against metal to metal contact.
If your engine suffers from any other issues (mechanical/combustion/tolerance issues), or your oil is contaminated with water or fuel, not even the best oil will protect your engine and failure cannot be blamed to the oil quality obviously.
ZDDP is there to ensure that IF the oil film is sheared both metal parts are covered with Zinc which will sacrifice itself and provide protection against the metal parts contacting and must be seen as a backup system only.
Therefore you will see that the better oils (with high film shear) do not have to have the highest amount of ZDDP as well.
ZDDP will, like most oil additives, reduce in quantity (ppm) over time during use and with that reduce the protection which gives the need for the oil changes.
All the additives content goes down during use, as is viscosity, increase of contamination and other factors that all together need to be considered when oil requires replacement.
For example, your ZDDP level might still be high, but the viscosity has dropped below standards which will force an oil change regardless.
The film strength of a particular oil film, or its exact contents of ZDDP or any other additive, is never provided by the maker for obvious reasons.
The tests done by this guy provide a clearer view on exactly that, for additives (dopes) contents in PPM you can send a new oil sample to a lab and have it tested for whatever you want and they will tell you.
As some guys do, you can send another sample after you have run the oil for 5000 miles / 2 races / 5 pulls or whatever you do with your car and see what is remaining of those parameters you are interested about to determine when an oil change becomes necessary. (based on low ppm, viscosity, water contamination, fuel contamination, particle count as example)
