At the few places I've worked I've found a large part of the training was company-specific or team-specific tribal knowledge (here's how you restart our service, here's how our data pipeline works) that was either not actually documented, or documented somewhere in a wiki and despairingly out of date or unfindable. That's arguably the fault of the team, but one of the companies (can't mention names) flat out said that it was one of their strengths to be a "storytelling" company.