Think about this...oil does NOT vaporize easily. Fuel does. Here is what happens.
When fuel is liquid, i.e., before it passes through the injector at high pressure, it retains the properties of a liquid. Meaning it WILL NOT BURN. Only fuel VAPORS burn! When it passes the injector it is atomized into ultra fine particles of liquid which then enter the combustion chamber and immediately become VAPOR, which is then ignited by the spark and BOOM.
If you have two stroke oil (or any oil really) mixed with the fuel, that is, DISSOLVED into the LIQUID fuel...and that relatively cool mixture is passed through the injector into a HOT combustion chamber, the fuel EASILY vaporizes while the oil is very resistant to becoming a vapor. The oil "drops out" of the suspension and actually sticks to the metals inside the engine, which is what actually provides the lubrication. Very little of the oil burns initially and much of it passes through the engine unburned. There is some left over oil on the cylinder walls as the ring passes by, which provide ring seal by filling in the microscopic gaps between the rings and cylinder, and lubrication because oil is, well...slippery.
Two strokes, which as most know, have no crankcase oil under the piston, meaning the crankshaft bearing, wrist pin bearing, piston ring(s), cylinder walls, and piston itself must get lubrication from the oil mixed with the fuel. This oil sticks to all the bearings, rings, etc., and lets the engine live a happy life. If all the oil burned right away, there would be none left to lubricate these parts and the engine would die a very fast and hot death, as the friction created from unlubricated metal parts literally melted and fused the parts together. Ask any two stroke motocross racer about the time they put straight fuel into the tank accidentally...and then tried to run a couple hot laps. In a two stroke, leftover oil DOES create a goopy mess and requires cleaning of certain parts such as exhaust port carbon buildup, power valve mechanisms (devices that change the port opening area/height/timing inside a two stroke), some of it does burn, especially in a cold engine, and is the reason why two strokes are not favored by the EPA.
That being said, a single ounce of oil per 5 gallons of fuel (640:1 ratio) is so incredibly lean a mixture, that I certainly see no actual harm in it. Hell, I have gotten home from the track on 5 gallons of gas left over from my premixed mx bike fuel, mixed at 4oz per gallon of fuel (32:1 ratio). Many times in fact...mx racing for a teenager was expensive, and left over bike fuel was a lifesaver many times
The reasoning behind mixing a little two stroke oil in your gas for a 4-stroke engine is sound actually. It WILL indeed provide a bit more upper cylinder lubrication since a bit more oil will be on the cylinder walls which would indeed help create a better ring seal. However, too much and then you WILL create MORE carbon fouling because some of it sticks around and burns, leaving, yep, you guessed it, carbon. The old beaters you see running around spewing blue smoke are burning the extra oil that is going by the piston rings, valve stem seals, etc., and those engines will still run a loooooong time. It's not ideal but it does work.
How much benefit you actually gain is a guess at this point and it would seem that perceived gains may actually be in the head. Until someone takes an otherwise IDENTICAL setup and dyno's it under the exact same temperature, load, etc., with oil and then without the oil mixed into the fuel, and can provide scientific results which show the differences, it will remain to be seen if it is worth trying in an engine such as ours. Actually, if you reduce the amount of fuel into the engine (which you are by adding oil to it) then the motor would make LESS power, although you may make gains in lubricity which would negate that miniscule loss. At 1oz per 5 gallons, you are running 1/640th LESS fuel into a given combustion cycle.