My Pixel 1 came with a blue USB 3.0 cable, which handles 5Gbps just fine.
Edit: The above sentence is incorrect, I misread a source. The original Pixel shipped with a USB-A to USB-C cable that supported 3.0 speeds and a USB-C to USB-C cable that supported 2.0 speeds. Since the Pixel 2 they only ship with USB-C to USB-C cables that support 2.0 speeds.
One could speculate that the moment Google knew their phone was a success, they stopped caring about open standards.