The new A4-9210C and A6-9220C are based on the old Stoney-Ridge series from 2016. Compared to the old non-C variants, the new APUs feature lower performance and clock rate to achieve a reduced TDP of 6 Watt. That, however could enable passively cooled devices.
https://www.notebookcheck.net/AMD-announces-two-new-Chromebook-CPUs.391766.0.html