How would it suck up more dust from underneath than it would from the sides? I don't see a major difference with previous models or competing laptops.
Also, desks and surfaces are usually cleaned.
Also, desks and surfaces are usually cleaned.
My MB Pro started failing for thermal reasons after 5 years, fortunately, the local service partner could clean it for a tip. After that, the thermals of the machine were distinctively improved.
Dust in the ventilation is just a matter of time, a machine should not fail because the user can't clean that dust.
Also, I think you are way overstating how dusty this will get. It's not going to be any worse than anything else built in the last 20 years.