The CPU Meter in the Renderer is a bit of a misnomer. The Renderer CPU meter doesn't meter CPU usage, but the time audio driver callbacks take to complete processing an audio frame. 

MacOS running on Apple Silicon doesn't allow audio applications to use all the processor cores. Instead, the macOS scheduler balances performance vs power consumption.  

The Renderer uses allocated threads in an "audio workgroup" for a given audio driver. The deadline for audio driver callback is 10.66ms per audio frame. The macOS scheduler running on Apple Silicon dynamically allocates cores as needed to keep the processing within the deadline while keeping power consumption down. The result is that the Renderer CPU meter on a Mac with Apple Silicon shows how much of an "audio workgroup" is being used but the number of cores dedicated to the "audio workgroup" varies given the processing load. 

The visual result is that the Renderer CPU meter often shows a higher value than lower powered Intel Macs that don't utilize an adaptive OS scheduler. There are generally more than enough cores on tap to provide processing as needed.