It is a big swing if you look at realistic doses intending to improve performance. The numbers you’re using for caffeine in that hypothetical situation is too low. The recommended baseline for dosage is 3mg/kg. Some can tolerate upwards of 5mg/kg or more. For someone that’s 80kg the difference in rates of metabolism could be the difference between therapeutic levels of caffeine, sub therapeutic and toxic at 4 hours post maximal absorption.
I think you’re responding to another person on the other thread. Not me mentioning the stuff about tolerance.