Several other articles more or less confirmed the sentiment of this one. With the quality of journalism these days I'm not saying this is accurate, but... Are you sure that both the PS4, Wii, and Wii U are all the same?
As a member of the video game industry media, I can tell you only too well that it's common for sites to report news without understanding what it is they are actually reporting (actually...regurgitating given that damn near none of them do anything more than rewrite press releases).
And as someone with a technical background, I can tell you that the properties of BlueTooth limit your connective devices to a total of 8. BlueTooth uses a piconet setup. Each device has a 3 bit address which means only 2^3 devices can be connected (8 total).
There is such a thing as a Scatternet which is an ad hoc network of multiple BluTooth piconets. The problem is that BlueTooth wasn't designed for this and even if you did use it, you would double your potential device totals. And since the XOne is limited to 8, not 16, it's not likely using a Scatternet...otherwise why limit it to the already known 8 that standard BlueTooth already supports?
And I know those other consoles support the same because they also use BlueTooth. Sony even announced 7 concurrent controllers for the PS3 way back when the system was announced (remember, the console counts as 1 device too).