I mean, B does make some amount of sense, if you realize that it's supposed to give you the maximum among the parameters (so you'd normally call it as Math.max(5, 3) === 5).

Well, and you can call that with zero parameters, because you can spread an array into it, which might have zero length. And then given these conditions, and if you don't want to throw an error, then -Infinity is kind of the least bad remaining option, as it's likely to generally work with the rest of your logic.