Looks like DeWalt and Porter-Cable (brands of Stanley Black&Decker) are starting to share some. No mention though of the motor / bearing / etc. differences inside, though, other than the variable speed on DeWalt
https://atelierdubricoleur.wordpress.com/2019/05/22/tool-brands-compatibility-good-news-compatibilite-des-marques-doutils-bonne-nouvelle/