I'm just new to this website (joined-up today), but I'll risk posting my first response on here here [any fans on here of Gertrude Stein's brilliant literary invention of repetition?].
The great thing about Science is that in 'doing it' one starts out with the simplest explanation first; reaching it by working from First Principles & going forwards from there. So, does Sculptor have a significant difference in physical & chemical microenvironments (humidity, dioxygen level, temperature, saltiness, etc.) between his two pits, perhaps occasioned by his job-type (or hobby) leading to the preferential & regular squeezing of one armpit more than the other? Skin microbiota populations & cell densities & proteomes (e.g., respecting catabolic processes in particular) can easily be affected by tiny differences in local parameters.