If the rates of the first place prize are low enough (which I'm assuming they are) there's a good chance that two won't show up on the same day unless a LOT of money is spent, because the chance of even ONE showing up is low.

Like, go full tinfoil hat if it makes you feel better and control your spending, but with these really really low drop rates it's going to be hard to get more than anecdotal evidence on whether it's limited to 1x drop or not (if you choose not to believe them when they say it's not).