I had a theory that this might be something enabled by Mac OS 12.1 - I've had it working on a M1 Pro on 12.1 beta, however on the latest 12.1 RC it didn't seem to be working. You need to ensure you have Mac OS low power mode disabled before testing. It's not clear exactly what is "causing" this, but I notice Safari is the same.
I wonder if Apple do any kind of "feature flags" or random feature enablement/disablement at runtime to "ease in" new features?