It's a manipulation of semantics, is all, nothing super shocking. So I'll take that, and raise you with a manipulation of statistical probability!
For me, I think it's a draw since it's a death battle between 2 people who operate on absolutes. One guy always wins, so statistically, he has a 100% success rate and a 0% failure rate. The other guy never loses. Depending on where he decides to put his chances to the test, he has a 0% failure rate, but his success rate can fluctuate.
In a situation where no other participants fight, I think this one would end in a draw-- both of them definitely have a 0% failure rate. So if one decides to throw a max-power punch at the other who is throwing a max-power punch, they have a high probability of landing either a fatal hit or a KO-hit. The fact that the other guy has a theoretically non-100% chance of winning is negligible. So, they knock each other out, or they both die in that regard, resulting in a draw. (A 1 to 1 if you will). And let's just assume one warps reality to make both of them go max power to settle this.