Knee jerk assumption without knowing what's behind it. If I had a mower with that engine, I would still change the oil.
However, there is some truth to the claim depending who buys such a mower.
For math purposes, at my first house, I mowed 34 times a year at most, the time mowing was 50 minutes and any trimming and blowing added to that, so 50X34 = 28.3 hours a year on the engine.
So for someone that has a residential lot and isn't putting tons of hours on the mower annually, the engine will last longer than people think. You still need to maintain the mower and add oil as needed.
Interesting video on it. Start the video at the 5:10 mark unless you wanna waste time watching dumb comedy.