This leads to the slightly more productive question: Is there a way to programmatically catch this case, and what would be the best way to handle it?
I can think of for example rendering all the form fields, only with some being off-screen. When they all suddenly get set to values (detecting autofill), moving them to the visible area to allow for checking and submitting them in a single step.
Thus: we design best so that the 99% have their expectations, developed painfully over years of dealing with shit websites, met with a minimum of suffering, and also so that the 1% find a maximum of purchase for the tools we use to improve our own experience.