I've heard this advice in so many words many many many times throughout the course of trying to learn audio engineering. It's invaluable--especially when it's so easy to hop on Google and say, "How do I get my <insert instrument> to sound more <insert adjective>?"Before digital editing, I did a few recordings with bands. I insisted we know our material cold before we walked into a studio - well enough that we could play them several times in a row without major mistakes. We didn't have the budget for lots of studio times and tons of editing. That's still a good approach.
Neil Young always said he was after a good recording of a great performance, not the other way 'round. Prepare for a great performance, let the guys in the studio figure out how to capture that. Don't try to edit your way to greatness.
And in some cases people will throw out advice that takes you in every which way but the right one without any context for what it is you've done and/or are trying to do.
Case in point, I was trying to mix a song a few months back and I was looking to get advice. I provided as much info as I could about what I'd tried and almost all the advice I got was on how to "fix" something that should have just been re-recorded.
When I started trying to get it to sound as close to right before all the studio tricks and such, I found that the studio tricks seemed to actually do what others suggest. But it's something most people don't tell you, but maybe it's implied and I'm just not very smart.
That's a very real possibility.