I think I would agree with you. However when I was a kid, I never used my desk to study. I studied where it was comfortable, which either ended up being on top of my bed, or on the floor - both of which had plenty of room to spread out my materials.

If a kid thinks they have to use a desk and never takes initiative to do something else, I think that would speak more to a kid's future success than the size of their desk.

If we just focus on environmental factors, I think higher ceilings and more-open spaces would also lead to success just as much as having a larger desk would.