> knowing the exact spec of your program up front is vanishingly rare, probably <1% of all projects

I don't have anything useful to add, but both of you speak and write with conviction from your own experience and perspective yet to refuse that the situation might be different from others.

"Software engineering" is a really broad field, some people can spend their whole life working on projects where everything is known up front, others the straight opposite.

Kind of feel like you both need to be clearer up front about your context and where you're coming from, otherwise you're probably both right, but just in your own contexts.