Yes. Essentially, "they were still the default projection from what was already known." was dramatically untrue at the time of 10% assessment, when it was not known that any neutrons are produced in fission, or any similar processes. And once it became true, Enrico Fermi did rapidly do a very difficult calculation of the neutron multiplication factor, and concluded that self sustaining chain reaction is possible.

The imaginary world where people of Enrico Fermi calibre are unable to follow simple steps due to the extreme conclusions, is a shared fantasy of many, many crackpots.