That depends on what the idea is. If you're selling software and you're a founder, you'd better at least want to understand your product or you are useless.
Understanding the product doesn't require to know in what language it has been built (unless you're selling a library that can be called from a certain language but I don't think that the kind of product we have in mind here). What you say is akin to a car salesman knowing how the car factory works.