There will be sloshing in the tank, and also there are vent tubes.

in real world driving does a 100% to the brim of the filler neck very high point above the tank lead to any leakage when the accelerations, braking, cornering, and normal sloshing are factored in?


It would be interesting to do a test for about 5 to 10 tankfuls when always just stopping the fuel tanking operation to mitigate that issue some with a slosh air pocket and then comparing those results to those from a road trip of constant fill to the brim refueling.

I would bet that the result, if any difference, would be withing the margin of error for winter/summer fuel, road conditions, temperature, ect. But it would be revealing if the result was an improvement. Then it would require further research to eliminate other variables.