The tactics of presenting a bus-powered hub as "self-powered" is a standard cheating practice.
The reason most manufacturers do this is that a certifiable bus-powered hub must have (a) power switches on downstream ports that don't engage until the hub gets enumerated, and (b) bus-powered hubs must obey power rules and system can enable only "low-powered" (<100 mA) devices, otherwise the power budget of upstream (host) port will be definitely exceeded. (USB3.0 has more reasonable power budget rules, but it is besides the point). The switches add a lot of cost, and 100 mA limit is a major inconvenience for customers.
As result, the Chinese industry invented this kind of cheating hubs, I call them "semi-self-powered hubs". Even if it doesn't have external power, they make its descriptors as it is "self-powered". It can't be USB-IF certifiable as result, and they can do anything with power distribution. I have one USB 3.0 hub that has about 800 uF total capacitance effectively loading its upstream port directly (while specifications allow no more than 10 uF total at the moment of connection).
This cheat also allows system software not to engage the power budget policing, so customers can connect any number of devices including those who consume 500-900 mA, and OS won't object to this. It works up to the point where the upstream (host) port can supply the load, and it might continue to work until the connector melts down or system power supply collapses or port overcurrent trips.
So yes, this brutally violates all good intentions of USB specifications, but it is quite practical.