Meh, I have exactly the same problem with Nexus 6p. I need one USB-C/USB-A cable for data transfer, another USB-C/USB-C for fast charging from the power brick that came with the phone, but back again to USB-C/USB-A to charge from the car. And don't get me started about the lack of good car charges that that support USB 3.1 PD.
It seem some friction to be inevitable when new physical connector is introduced.