No actually. There was a second way of winning: make up your
own secret. Nothing stops anyone from thinking of the magic formula for himself. It's also perfectly possible there is an even better way to go from number to roman that nobody discovered yet.
And if a person would also have found the magic formula if he
hadn't known the existing one, I don't think you can say he got an unfair advantage from it. I know I would have found it, and Juho might or might not have, but at least he has come up with magic formulas before. And third place was easily possible without the magic formula.
And let's be very clear that all this was an accident. When making up golf challenges, one tries very hard to come up with new ones where old golfs cannot be reused. Nobody wants
a perl golf where the real work consists of searching the web instead of programming.