He’ll bury his preconceived notions about this once he’s deeper in school. Some “design” engineers do routine iteration of the same thing over and over and some testing engineers get to conceive and build unique testing fixtures often. They also get to tell the product designers how to fix their stuff. There are a LOT of angles into being able to create, which is essentially what he’s saying by “design.”
Also, not sure why he feels BME is the best avenue, unless he’s interested in biological systems. ME is much broader. As I understand it, BMEs often need advanced degrees to do the type of work he’s alluding to.