As said above, this is marketing...
For a power washer, you will use it 5h par season ? And you have a good chance to not winterize it and crack the pump in 5 years... so even without topping the oil the engine will outlast the machine :laughing:
To be more serious, if you want to take care of it change the oil after some x hours (others here know better than me interval times) or 2 years, depending of your usage. If you don't care that much just top the oil. (If you don't care at all you would not have asked here).
I like my equipment, I just change the oil today on my push mower. Probably 20h a year. Cost me 6$ to change the oil. It worth it doing it every year for a 1000$ mower in my opinion. Even if the deck will be shot before the engine, this mean a good running engine, no smoke, good power for 15years.