Expected-cost reasoning treats errors as interchangeable and asks only how often each occurs. That is the right frame for most of this work: a wrong guess about a function’s behaviour costs one round trip, and guessing well is therefore worth something.
It is the wrong frame when one of the outcomes lands on a person. Misgendering someone, deleting what they cannot recover, publishing what they meant to keep — these are not more expensive versions of an ordinary mistake. They are a different kind, and no frequency argument reaches them, because the neutral alternative does not have a bad tail at all. A guess that is right nine times in ten is still a mechanism that will land on somebody.
So the rule is not “be careful” — care is not a mechanism. It is: where a choice has an option that cannot produce that outcome, take it, and stop computing which is likelier. That is why some of the rules here are absolutes rather than defaults, and why an absolute is worth the occasional stilted sentence.