Maybe a bias. Losing a non-paying "member" doesn't lose much. OTOH, I was a non-paying member for several months while looking around and playing. I heard some complaints about cheating, but in my 20-some games don't really have any suspicion that any of my opponents were doing so. My losses were due to my own errors.
There is no way to really answer that question without an admission from the top brass. Since we have no idea of how cheaters are caught or identified, and since evidence is kept private, presumably to avoid divulging methods of detection which is reasonable, I guess we simply have to take their word for it.
From a practical standpoint, if someone was cheating, why risk membership money by getting caught. If we could possibly know the true percentages of member vs. non-member cheating, I know where my money would go.
i have read more than once in various places on chess.com where someone claims that chess.com is less likely to ban premium members than non-paying members. is there even a grain of truth in these claims?