I too am not knowledgeable about aerodynamic myself but my educated guess is because of efficiency. Moving horizontally , energy is conserved by lift. You would need more energy over longer periods of time to fly vertically which is why planes stall when they try to climb to high to fast. Also the higher up you go the thinner the air meaning you would need combustion to get any higher at some point as there would not be enough air to push to keep you up.

Over extrusion and first layer to close to bed.

Adjust z oddest 0.05mm and see if it still happens. You might also calibrate your e steps if you still see issues.

I wonder more the average life expectancy or even the percentiles. What the max age does 90 percent of the population reach.