Some parts of the paper are available here: https://www.sciencedirect.com/science/article/abs/pii/S0896627324008080?via=ihub

It doesn’t look like these “bits” are binary, but “pieces of information” (which I find a bit misleading):

“Quick, think of a thing… Now I’ll guess that thing by asking you yes/no questions.” The game “Twenty Questions” has been popular for centuries as a thinking challenge. If the questions are properly designed, each will reveal 1 bit of information about the mystery thing. If the guesser wins routinely, this suggests that the thinker can access about million possible items in the few seconds allotted. Therefore, the speed of thinking—with no constraints imposed—corresponds to 20 bits of information over a few seconds: a rate of 10 bits/s or less.

The authors do draw a distinction between the sensory processing and cognition/decision-making, at least:

To reiterate: human behaviors, including motor function, perception, and cognition, operate at a speed limit of 10 bit/s. At the same time, single neurons can transmit information at that same rate or faster. Furthermore, some portions of our brain, such as the peripheral sensory regions, clearly process information dramatically faster.