But that's an arbitrary constraint choice that didn't need to be there. It's not inherent to the medium. He has a justification for it (curves are "flimsy and introduce variances") but that is easy to get around with perpendicular reinforcing pieces inside that constrain the curve.

Arbitrary constraints are essential to any artistic endeavor. It's foundational to fostering creativity. So yes, it's an arbitrary constraint. That doesn't make it any less valid.