They are making these claim using the EEMBC benchmark. This must be an interesting benchmark as they claim the fastest chip on the EEMBC benchmark is a Cortex-A9, a 8 year old design.
"The M1 chip is roughly the equivalent of 10,000 CoreMarks in EEMBC terms; divide this by eight cores and 15W per core, and that is less than 100 CoreMarks per Watt."
Unless they think that the M1 is drawing 120W?