Isn't it expected that mentoring is fundamental part of being a senior worker? Usually "employer" don't know nowhere nearly as much about code as senior devs.

Isn't it expected that mentoring is fundamental part of being a senior worker? Usually "employer" don't know nowhere nearly as much about code as senior devs. If somebody was hired purely to do onboarding, they wouldn't have good grasp on the code either. Seniors who have up-to-date knowledge of the is best bet, no?