NEW RESULTS! Cosmic Quantum Bell Test

I have a confusion about the nature of observation, which could resolve another one I have about entanglement.

How has it been determined that the particle really remains in a superposition of the two states until it has been observed?

If the superposition is what the mathematical equations imply, couldn't it be that it is the limitation of the theory to provide us probabilities of two the two states (or how much of each state is part of the superposition), but in reality, there is a definite state which we only find after observation?

Thanks in advance.