Many directors started in other roles in the movie industry, typically as writers, PAs, or other subspecialties. Chad Stahelski was a stuntman and stunt coordinator before he started directing John Wick, and it really shows.

I think the clear distinction is between someone who understands a part of the job, and someone who is good at part of the job. If you don't understand how costuming works, as a director, you're going to have a hard time getting good costumes, but by no means does that mean you're able to pinch hit in that role. I personally believe that it's difficult to replace hands on experience as a way to truly understand something.

In software engineering, I think there's a huge gap between managers who worked in some other industry and transferred over, versus having previously been an engineer, even a mediocre one. Knowing how the sausage is made is hard to replace.