Earlier quoted context omitted.
I don't think AirBnB remotely fits the notion of a 'flophouse.' https://en.wikipedia.org/wiki/Flophouse
https://www.airbnb.com/rooms/23131937 10 people per room.
As the Wikipedia article I linked states, flophouses were typically rented by transients -- what we generally call "the homeless" these days. The term "flophouse" originated with hobos and propagated out to the larger culture.
I was homeless for several years. The prices listed in the thing you linked are comparable to what I sometimes paid for one night for a hotel in Fresno.
There are people these days who are without permanent residence who live in hotels. Some definitions of homelessness count them as homeless.
What you linked really doesn't fit what I am talking about. I have seen articles about illegal rentals stuffing multiple people into one room in big cities. They usually found them via Craigslits, iirc.
Most AirBnB listings are along the lines of the cost of a hotel or more. From what I gather, they wind up being a hotel alternative in most cases, not something dirt cheap with no amenities that a homeless person might rent for a night or two.
I blog about homelessness. I still talk to homeless people at times. I've had a college class on homelessness. I'm not uninformed on the topic of homelessness and what homeless people today are doing to get by.
AirBnB rentals are not some bog standard coping mechanism for today's homeless, from what I gather.