Ummm, might want to correct that original post. Of course energy is dissipated when the frame flexes. Where do you think that energy comes from?

If what you actually mean to say is it might not matter to some people that’s fine but the laws of physics do indeed apply to bicycles. I, personally, prefer a steel frame because, yes, it flexes more than aluminum. Can I measure it? I doubt it and I don’t care.