Certainly the past about Picard gaining command due to his skipper's death directly is apocryphal...
Actually, it's not. In "Tapestry," Q allows Picard to see how his life would have turned out had the stabbing incident with the Nausicaans never happened. Picard is horrified to find himself trapped in a dead-end job as an astrophysicist. He confronts Q, who says that because the stabbing incident never took place, Picard never developed the courage and resolve needed to get noticed by his superiors. It's then that Q mentions Picard saving an ambassador and taking command of Stargazer's
bridge after the death of its captain. It's not clear when this happened, but it's clear that it did.