>> Both achieve nothing unless you can actually sell what you have built.
I both agree with you and disagree. As a technologist, I agree sales are the only thing that matter. Most technical things are easy to me, and ultimately they are just code unless they can be monetized.
But I disagree on the value question -- they are only valuable if they are being done before the build-out. If there is just a promise of sales after free upfront effort from a technical co-founder, then the value is tenuous.
A good Business Co-Founder would be selling early, ideally at concept phase, such that there is no question of value becuase you already have pre-sales or purchase orders.
If the non-tech guy says "Here is my idea for a product. I've been working in this domain for 15 years and I know what the pain points are. I have XX customers that have expressed an interest and paid a deposit (or committed to pay once the company starts)." then that I think is worth something.
Ideas are important. Building a product is important. Both achieve nothing unless you can actually sell what you have built.