All oil starts the same.
It gets broken down into parts, filtered cleaned then reassembled.
Air cooled engine oils are specifically formulated for air cooled engines that have higher range of running temperatures.
They also have a lot of moisture dispersants & anti corrosion addatives because mowers & most air cooled engines sit around for months not being used.
Automotive oils are designed to work best in an engine which runs between 80 & 120 deg C and is fairly constant temperature all over due to the water cooling.
Water dispersion is not a big problem as the engines usually get used daily or at least weekly all year round.
Putting the 3rd best choice into your engine will not make it blow up.
At worst it will allow excessive corrosion during the off season & may knock a few hours off the engine life.
At best it is just costing you more .
The most important thing is how often you change it followed by when you change it.
Mower engines are low speed engines so suffer higher loads than auto engines many of which now days idle near the actual running speed of mower engines.
When something like a cam follower rubs on a cam, it relies upon the oil to maintain a film between the 2 of them.
The faster this happens the easier it is for the oil to remain there.
The slower it happens the greater the chance of the follower running dry by the time it is on the lowering ramp of the cam.
There are a squillion little things like this and that goes a long way to understanding the difference between an engine that does 5,000 trouble free hours and one that is worn out in 500 hours.
Now I only studied oils in one unit that was 2 hours a week for 13 weeks and in that time we covered oils, greases, cutting fluids & coolants so an expert I am definately not.
However that has given me enough knowledge to understand the difference between oils and to realize that 120% of all the advertising is pure bull.
Now 99.99% of the people who rabbit on about oils have never had 1 minute of formal education about lubricants and in most cases do not actually know the meanings of terms like "Detergent" and the difference between a detergent & a dispersant. Even fewer can understand oil test data, let alone what they mean to their engines.
You car run your edger on light machine oil SAE 0 to 10 if you really want to.
All that will happen is you will burn almost all of it every time you use the trimmer and you will be paying $ 50 /qt for it.
So no matter what the engine is, the best oil will always be the oil that was specifically blended to do that job.
Lots of other blends will also work, and some will be better than others.
OTOH finding a single oil that is OK for everything you own and using it on everything again will be fine just so long as it is changed at the recommended interval if not earlier.
The big problem comes when someone puts a fully synthetic 50,000 mile change interval oil into a mower and decide it never needs to be changed.