I got your point. You argued explanations don't have to be mutually exclusive, and I was say in a vacuum they don't have to be, but if we recognize certain details, considerations, or facts to be true or valid, then different explanations can and often do become mutually exclusive. You can either craft the explanation to fit with known circumstances and conditions, or reject the premises of those conditions and circumstances, in which case you'd have to make an argument for why.
I presume by falling back to a bromide about how each side has different assumptions so we can't know for sure which explanations are right you are trying to reject or at least cast question of the specific circumstances or conditions that would suggest your explanation is in fact mutually exclusive to other explanations and the basic facts and details I posited in my earlier response, but you didn't actually present any reasons or mount any arguments for *why* the premises behind the arguments counter to yours might be false or wrong.
Note, this isn't simply a matter of two sides making different assumptions. We do have, at least on some presumptive basis, actual facts and details that we can probably regard as sound and dependable. For example, anecdotes about China trying to negotiate down the number of planes they were buying or Russia refusing to localize the Su-35's avionics or open its systems to allow for integration with China's aren't matters of fictional speculations. If you're going to reject these details in how you formulate an explanation for the purchase you're going to need to explain your rationale.