We hired someone strong and watched them stall for two weeks on our payments service. That gap was ours, not theirs. The things they kept asking about were the things nobody had written down, and we only noticed because a newcomer said it out loud.
Now week-one questions go into a list we fix, instead of a ramp-up checklist we forget about. You can read a new hire's confusion as their problem, or as a hole in your documentation.