I'm having trouble believing the 10 bits/s claim. That surely can't refer to the collective output of all motor neurons, can it? Athletes and musicians are sure

I'm having trouble believing the 10 bits/s claim. That surely can't refer to the collective output of all motor neurons, can it? Athletes and musicians are surely outputting a rate of motor data at least 4 orders of magnitude greater than that. Even people who are sedentary at a desk surely output more than 10 bits/s of motor signals. Or perhaps the author wants to narrow it to the average rate of verbal thought creation. But even then, I can think of counterexamples. Any insight what this is actually referring to?