But he had not been an apprentice before making this, he started the apprenticeship that year, and this is supposed to be the first thing he ever painted.

> Michelangelo's biographers—Giorgio Vasari (1511–1574) and Ascanio Condivi (1525–1574)—tell us that, aside from some drawings, his first work was a painted copy after a well-known engraving by Martin Schongauer (1448–1491) showing Saint Anthony tormented by demons. Made about 1487–88 under the guidance of his friend and fellow pupil Francesco Granacci, Michelangelo's painting was much admired; it was even said to have incited Ghirlandaio's envy. [https://www.metmuseum.org/exhibitions/listings/2009/michelan...]

I can’t respond much too this being Michelangelo’ painting, but if he was an apprentice under his fellow pupil it’s possible that he just did minor things or filled in. It was how you learned. You did final retouching and such.