Not cynicism
I tried to clue y'all in and gave you the info to confirm for yourselves, but cynicism won out over a rare case of free money.
Not cynicism. I believe this was a real op, and probably people have won money with it.
The trouble with arbitrage: execution risk (chance line will move as you actually make the bet), getting a diammetrically opposite lock (no chance of losing both bets due to differing rules and regs), tieing up money, and a dozen other practical problems. Like many, I initially thought arbitrage was the key to the vault only to discover it is mostly a second-tier advantage play due to these difficulties. Small arbs occur on a daily and ongoing basis in all kinds of sports. Large arbs like this are less common but are not that hard to find for the patient.
If you had been clear about the nature of the op before your post scrolled down the page I would have taken you up on it. Even then, I wouldn't have played it as a straight arb because it was worth peanuts. Give me detail next time, if there is one, and I'll send a bunch of guys and referral money your way.