Sorry... that is not true.
Less oil in the gas means the... gas to air... actually gets richer (because there is more gas, less oil), which is the opposite of what the guy needs.
Example.. (the numbers are off a bit to make it easier to understand)
The air going into the carb is 100% air.
After it goes thru the carb it is 90% air, 10% fuel.
But say the fuel is 95% gas, 5% oil..(20 to 1)
Then overall mix is.. 90% air.. 9.5% gas..and half a percent oil.
Then cut the oil in half (40 to 1)
Now the overall mix is...90% air.. 9.75% gas.. and quarter a percent oil.
So you can see there is now more gas to the same air... it's RICHER.
When knowledgable people say "lean it out", they mean put a smaller jet in... not decrease the oil.