When you say "...are supposed to be paid using earnings...", are you referring to a legal requirement? If so, this could be stopped by someone with a legal challenge.
If you just mean traditionally, well, if this is a more efficient way to meet the various goals of all parties to the transaction, I'm with founders/investors/innovation, moreso than tradition.
Also, money is fungible. What if AirBnb has earnings from elsewhere that could pay the dividend, meeting the early shareholders' desire for a interim diversifying return? But, that would then leave less capital for expansion. However, new investors are happy investing money that replaces (and then some) the cost of the dividend to support expansion costs.
There'd then be no essential violation of the way you think things are 'supposed to be': just think of earnings paying dividends, and then new investment adding all required expansion capital. Everybody who's a party to the transaction is happy, in a tax/legally-efficient manner, and no one's rights are trampled.
(As I've mentioned elsewhere, I think the main fairness issue would be if anyone who had the legal right to become dividend-eligible, for example by vested option-exercise, wasn't given that chance. But that's an internal fine detail we don't know about this still-in-progress private company financing.)