It's the theoretical "retractable dog leash".
You sometimes have to let your copilot take a wrong turn and as he starts to run the length of the leash (or your ability to safety guide him back to where he should be), you interject. People learn by doing. You're never going to be a chef, if, as a line chef, your boss always says, "Well, you're going to end up cutting or burning yourself so I'll make all the decisions and you simply carry them out the way I say do them".
Every captain on earth says "Oh, we'll do things by the book" but it's laughably idiotic because there's very little by way of a feedback loop that we have so a lot of us aren't operating via SOP and don't even realize it. Then the poor copilot has to play chameleon and constantly choose between "I haven't seen that procedure before and I can't find it in 'The Book'" or being complicit and complying with whatever the captain is doing or expecting you to do.
One of the best lessons I've learned is that it's not about "me", it's about my crew. If they're able to feel empowered to do the right thing, communicate and be transparent about it, everyone wins. No one is going to perform brightly for a pot-bellied angry tyrant.