[ncray]

5000:1 means 1/5001. Assuming independence gives (1/5001)^2 * (5000/5001)^2 * 3 = 25000000/208500050006667 = 1.19904x10^-7
17mil:1 = 5.88235x10^-8
Edit: there's no stipulation that the other 2 players can't also ace, but that just changes the 5000/5001 to 5001/5001, so there's hardly a difference

So if they didn't screw up the math, they're saying that one person getting a hole in one is not independent from another in a foursome. According to them, if one person aces, the next is less likely to than if he were just shooting alone.