I know you're joking, but the number of steps is well defined and doesn't vary as it's essentially a difference. The difference between two numbers is always the same regardless of whether you're using a 0-indexed or a 1-indexed base system. E.g. regardless of whether you call an element in an array [1] or [2], it's still two elements away from whatever is [3] or [4] -- the number of stairs climbed is the same.

So you're free to use either top-stepian or bottom-stepian notation when counting stairs and you'll get to the same answer either way. So it's just an implementation detail that's left undefined in the spec.