Yes, there are a very large number of calculated possible functional cytochrome c sequences. (2.3 x 10 93rd power). Therefore the random chance occurrence of a high degree of similarity between any life forms would be remote (more remote than the number of estimated atoms in the universe).
This is strong evidence against RANDOM chance as an explanation for cytochrome c similarities in living things.
However, evidence against random chance does NOT equate to evidence for “common descent” between creatures.
For example all the possible hypothetical software sequences making up iPhone iOS software would be a much larger number than the above figures for cytochrome c. Yet the similarities between various generations of iOS are not evidence for “common descent” via naturalistic mutational processes, but instead due to being the product of a common intelligent design source.
The evolutionist “protein functional redundancy” argument is built on the assumption that the only options for cytochrome c similarities are random chance or common descent.
The evolutionists are using “evidence” against one naturalistic scenario as “evidence” for another.