This is an argument about social perception. Once you get over the fact that some community on the internet does this thing, and you think that community is weird (and therefore the thing itself is also weird), you may observe that all human actions are implicit bets on various beliefs. Explicitly wagering money is just a special case of making certain narrow beliefs much more legible.

I agree that in practice, it's pretty likely that the author of the piece refuses to bet at least in part because betting substantial sums of money on outcomes that are non-central subjects of wagers (i.e. not an explicit game of chance, sports, politics, etc) is socially unusual. But I also think that if he was very confident he'd be happy to take the money.