I forget which painting or statute he did but it had a pinky finger flex and the associated muscles in the forearm corresponded with the flex according to medical experts. His working with bodies of deceased helped him with such details. I read a biography on him and he was genius but could be lazy with patron commissions. I forget how long it took him to paint the Mona Lisa.
For a fine artist of his quality, ‘being lazy’ was probably a passive aggressive tool of negotiating for a higher price.
Most likely, Leonardo was his own huckster and manager.