It is entirely the traveler's responsibility to understand the requirements for stay and local laws of a foreign country. Ignorance can only get you so far.
The immigration officer – who has absolute power over entry – neither asked anything unreasonable of him nor made any false accusations. This is despite the reporter technically having broken the law. He got off lightly, since the fine for not registering within 24 hours after arrival can be up to $300.
When you break the rules (intentionally or not), you're taking a risk. Some people get off unnoticed whereas others learn the hard way. Ask people familiar with the country and its laws before arrival and plan your trip properly.
The sexual relationships is relevant because foreigners in China have a reputation of sleeping with a lot of girls, and this leads to a lot of resentment from many of the Chinese. If they at the airport can so easily see when/where a foreigner stayed at an AirBNB, then you have to wonder what other info these people, as well as the embassy people approving VISAs, can see. They do not need to give a reason for denying entry, so it seems it's only a matter of time before they're provided with even more private info that will most definitely be used against foreigners.
Tell me, which countries have you visited throughout your life, and what does the law state regarding staying at an AirBNB residence at each of these countries? Would be great if you could provide official source as well, I mean it sounds like it's very easy for you to look it up, so I assume you don't mind. If you don't want to reveal your travel history, then you can use this list: Germany, France, Iceland, Ukraine, Vietnam, Thailand, South Korea, Cambodia, Japan.
Thailand does not require registration, but authorities prevent travelers from re-entering shortly after their stay (cracking down on "visa runs") which has caught some tourists/nomads off guard. The strictest punishment is banishment for a maximum of 10 (IIRC) years.
Like China, Japan requires registration with the local city office if you are staying with a long-term visa. Although it should be noted that China applies this to all visa types whereas Japan allows tourists to stay without registration. Failing to register with the local Japanese city office can result in banishment.
As with registration in China, you are not told this information upon entry of these countries. If you blindly travel you will be caught out (and usually punished). However, asking around and doing the research before you travel can prevent that from happening.
I've spent about 10 years living in various Asian countries, including China, and I have never met anyone who would bother to register whenever they changed apartment. I'm also certain if I asked all my contacts in China, then none of them would know anything about it.. and I'm talking about hundreds of people, including students/professors at their best universities. You greatly overestimate the amount of info you can get by doing research/asking around when you go abroad.