Need thoughts on tribal knowledge

I've noticed this to be a common experience amongst employees in tech (men & women, alike) that there is sometimes one person on the team who is the designated "genius" or "wiz." This means they've been on the team since the start and they know everything and very little is documented (or it's outdated). So essentially this person has their job because they're gatekeeping the knowledge needed to work on this team and to keep the team running. You have to ask them every little question rather than referring to the documentation.

I'd love to know if you've experienced this at your company.