Software development topics I've changed my mind on

Nah.

I (16+ years developer) prefer to iteratively go between coding and designing. It happens way too often that when you're coding, you stumble across something that makes you go "oh f me, that would NEVER work", which forces you to approach a problem entirely differently.

Quite often you also have eureka moments with better solutions that just would not have happened unless you had code in front of you, which again makes you approach the problem entirely differently.

He might have meant design, and I'm not sure about that.

But the other thing i think of is: Understanding the problem.

It's hard to do too much of that before you start coding, and easy to do too little.

It overlaps with design to some extent, because once you understand the problem better, some designs will naturally seem inappropriate or better -- without having to spend time allocated to "designing" necessarily, just when you design you're going to come up with things that work a lot better the better you understand the problem you are trying to solve.

How the stakeholders see it, and what's really going on, and why it's a problem, and what would make an acceptable solution, and what the next steps down the road might be.

Programming is specifically about the authorship of code.