Qualcomm says Quick Charge is connector-independent, and there have been no reports of malfunctions using the technology over USB Type-C.
There's been some discussion about the and using Qualcomm's through the USB Type-C connector. In particular, Google's Benson Leung — a popular USB Type-C evangelist of sorts — over the USB Type-C specification, and many have expressed safety concerns about mixing the two technologies.
We reached out to Qualcomm for an official statement, and they replied.
Qualcomm Quick Charge is designed to be connector-independent. It can be implemented in a device that supports a variety of connectors, including USB Type-A, USB micro, USB Type-C, and others. When an OEM chooses to implement Quick Charge into their device, they can configure the voltage to fit within the specifications of the USB Type-C standard. We have received no reports of user experience or device malfunction issues with or without USB Type-C connectors. At Qualcomm Technologies, we are continuously working to provide the best solutions for our customers and consumers. Qualcomm Quick Charge is a leading edge fast charging solution with more than 70 devices and 200 accessories supporting one of the two most recent versions of Quick Charge, with even more currently in development.
While this doesn't directly address any violations of the specifications, it certainly sounds like the devices in question are engineered to be safe and charge rapidly via Quick Charge over the USB Type-C connector. It's also worth noting that both the phones and the chargers themselves have been UL listed and CE Mark certified as safe when used as directed.
As always, we recommend that you use the charging components provided by the manufacturer or certified replacement equipment at all times. Some of our phones can draw enough current to be dangerous if not used correctly. Be safe.