To self-identify as a polymath would be an utter nonsense disproving the claim.
This claim was made in a discussion on RG. According to the OED, a polymath is "a person of wide knowledge or learning." In some cases, people seem to consider polymaths as being experts on a lot of topics, but that isn't universal. Given the basic definition, it doesn't seem like it is absurd to be able to recognize oneself as a polymath, but perhaps there's more to it than that.