Sorry but are you really citing the problem of “not double booking” properties as one of the reasons Airbnb needs to hire an army of web developers?

“How many developers does it take to design a reservations schema?”

I would put open source projects like the ones you’ve mentioned as more evidence Airbnb has too many idle engineers. I think even Google uses Tableau for their BI analytics stack. There’s not necessarily any business justification for a private startup to have to build that from scratch, and the only way Airbnb could justify working on projects like that is if they had a ton of engineering capacity not already working on the core marketplace product.

Most if not all of the challenges you listed are non-engineering related (legal, compliance, host operations, localization)