Whether this is actually true or not remains an open question, but it is indeed the expected consequence of QM. However, there is as yet no experiment showing a

Whether this is actually true or not remains an open question, but it is indeed the expected consequence of QM. However, there is as yet no experiment showing any kind of quantum behavior for huge objects (closest is a few hundred million atoms as far as I know). Still, the point was about a classical model, not about physical reality being classical or quantum. To rephrase, my point was that even in a classical model there are quantities that can't practically be measured (even though classical mechanics as a model assumes all objects have definite positions and momentums), and that doesn't stop us from accepting in such a model that they are 'real'. So, the idea of property that is 'real' but not really measurable already exists in classical physics, it is not an invention of exotic interpretations of QM.