Maybe a good idea for thost very old motors with carbs and without electronics or catalytic converters.
Bad idea for any fuel injected vehicle with electronic sensors (especially an oxygen sensor), an EGR valve and a catalytic converter.
You just can't compare the two. It's like saying "I have a friend with a very old truck that still uses leaded gasoline and it runs fine. Should I use leaded gasoline in my new truck also?"
Look at it this way, your friend has a truck that is 29 years old and has only 200,000 miles on it - an average of less than 7000 miles per year. That is less than half the average annual mileage of 15,000 miles per year. I put on close to 200,000 miles on my vehicles before I sell them and it only takes 8-9 years to do it and I've never had the problems or needed whatever benefits a squirt of 2-stroke oil is supposed to provide.
Cheers - Jonathan