Google opposes proprietary phone fast-charging
Google isn't a fan of non-standard approaches to fast-charging Android phones over USB-C, like Qualcomm's Quick Charge 3.0, and it wants manufacturers to fall in line. The newest Android Compatibility Definition document says it's "strongly recommended" that device makers don't support proprietary charging technology that modifies voltages beyond standard levels, or otherwise creates "interoperability issues" with standard USB charging. The company warns that later versions of Android might even require full interoperability with standard chargers.
This doesn't mean that you won't see fast charging. Both of Google's Pixel phones can top up quickly. However, it's evident that Google would like to fulfill USB-C's promise of cables and chargers that always work together. It doesn't like the idea that you might have to carry a specific charger for your phone to work as expected, or that a flaky cable might fry your charger, phone or both.
This doesn't mean that you won't see fast charging. Both of Google's Pixel phones can top up quickly. However, it's evident that Google would like to fulfill USB-C's promise of cables and chargers that always work together. It doesn't like the idea that you might have to carry a specific charger for your phone to work as expected, or that a flaky cable might fry your charger, phone or both.