They are still using the SurfaceDock with the SurfaceConnect Cable: https://www.microsoft.com/en-us/surface/accessories/surface-... , which does basically the same as USB-C. In an era when even Apple is rumored (and even if false, still plausible) to be switching to USB-C for the iPhone, Microsoft still tries to force a proprietary connector. Didn't they learn anything from IE? Even if it's good for them for a while,…
USB-C just isn’t popular enough yet to have crashed and burned (though even after that it’ll still be popular for ages for want of an alternative).
I have a Surface Book (the hardware was good enough to get me to switch from Linux, without ever actually having seen one), and the Surface cable is marvellous. Magnets are awesome, and the Surface Book is probably the most carefully magnetically-designed computer hardware. At work I have a Dock and I pretty much just put the Book on the desk by the connector and it jumps into place and my external monitors connect. And removing it, really easy and it can’t go wrong. The whole thing is really, really nice.