Ken, please don't go - we may have different views on hybrid, but I've enjoyed your thought-provoking contributions to this thread...
Is it really?
It is well known that Bernini had a workshops and statues generally attributed to him (such as those on the Ponte Sant'Angelo in Rome, or the ones on the Four Rivers Fountain) were actually designed by Bernini and sculpted by other sculptors, which are well known as sculptors of those works.
Antonio Raggi, Lazzaro Morelli, Paolo Naldini, Cosimo Fancelli, Girolamo Lucenti, Ercole Ferrata, Antonio Giorgetti, Domenico Guidi for the statues on the bridge, and Giovan Maria Franchi, Giacomo Fancelli (brother of Cosimo above), Claude Poussin and again Antonio Raggi for the Rivers are the well-known sculptors for those statues, carried on on design by Bernini. No such sculptors are known for Michelangelo's works to my (limited) knowledge.
I have never heard anything of the kind regarding Michelangelo, and gave for granted that his (relatively small) production was actually personally chiseled by him. I would not rule out that he made the design, some student made the "sbozzo", the raw work, and then the Master would make the real chiseling work. That would mean in any case that Michelangelo did actually chisel the Pietà, David, Moses etc. himself. Any pointer to further information regarding this is welcome.
Bernini himself did sculpt statues himself. For instance the Angelo con il cartiglio on Ponte Sant'Angelo was sculpted by Giulio Cartari and Bernini himself, another "copy", the original one of the Angelo con il cartiglio was sculpted by Bernini and his son, but was not paid by the pope and was kept by Bernini (there was some row over the interpretation of the agreement) and is now in the church Sant'Andrea delle Fratte. Same destiny for the Angelo con la corona di spine, the original sculpted by Bernini with his son was not delivered, the one which was delivered was the "copy" sculpted by Paolo Naldini. The Estasi di Santa Teresa is considered by Bernini and no aid name is known (again, some preparatory work might certainly have been performed by some aid).