It doesn't require an actual sphere, just an object that can be approximated by a sphere. You worm around this by saying the objects to be compared have the have the same proportions and same average density.
That's the trick, isn't it? I did some calculations using real birds of the same type and found weights overpredicted by thirty percent. How can you defend screwing with the laws of physics based on reconstructions of animals from a bone fragment?
But the real argument killer is the wing loading of your giant teratorn -- the real one. If You think things weighed less at the surface of the earth millions of years ago, why is the wing loading of the teratorn exactly in the middle range of modern birds?
Source? Authority? Link? PROOF!
why is the wing loading of the teratorn exactly in the middle range of modern birds?
Put MUSCLES on that wing and move it... with a 170 lb body hanging from it.
The Square Cube Law IS a law of Physics... how can you defend ignoring it?