How could theoretical physics without experimentalists aid distinguish observer effect from Kennard's uncertainty principle?

Question

Regarding this experiment which was carried out in 2012:

https://arxiv.org/abs/1208.0034

I'm wondering how could the scientific society be totally convinced(prior to this paper being published) based on a purely theoretical ground that the Observer Effect is not the true content of Kennard's derivation of Heisenberg's uncertainty principle, notwithstanding that his derivation doesn't resort to interactive measurement( measurement with light being shed on a system or whatever you like).

Since one could still stick to a view on QM which considers the theory as the theory of measurement and not an intrinsic and interaction-free general theory so that even Kennard's derivation can be considered as merely a semantical flourishing of the "observer effect" rather than a theoretically vital refusal of the "observer effect".

I mean one could still take the position that QM is intrinsically inclusive of interactive measurements that are carried out to exploit information about a system, no matter if the language and semantics seemed to be ignorant/independent of any interaction. A view that considers QM as an effective theory of measurement that has interaction implicit in itself.

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I guess it's not bad to share the abstract of the paper itself which doesn't leave space for ambiguity:

While there is a rigorously proven relationship about uncertainties intrinsic to any quantum system, often referred to as “Heisenberg’s Uncertainty Principle,” Heisenberg originally formulated his ideas in terms of a relationship between the precision of a measurement and the disturbance it must create. Although this latter relationship is not rigorously proven, it is commonly believed (and taught) as an aspect of the broader uncertainty principle. Here, we experimentally observe a violation of Heisenberg’s “measurement-disturbance relationship”, using weak measurements to characterize a quantum system before and after it interacts with a measurement apparatus. Our experiment implements a 2010 proposal of Lund and Wiseman to confirm a revised measurement disturbance relationship derived by Ozawa in 2003. Its results have broad implications for the foundations of quantum mechanics and for practical issues in quantum mechanics.

Answer 1

The easiest theoretical way to see that the uncertainly principle can't be explained by interaction with the measurement apparatus is just to note that the uncertainly principle applies even when there is no interaction with the measurement apparatus.

For example, if you put a thin cloud chamber in the path of a wide coherent particle beam, you'll see short particle tracks that are localized in position, and downstream from the cloud chamber the particles will have a wider distribution of transverse momenta, at least as wide as required by the uncertainty principle. If there's a small hole in the cloud chamber, then particles not detected by the cloud chamber (which therefore must have gone through the hole) will spread out transversely downstream from the cloud chamber in the same way as if they'd been detected by the cloud chamber at that location.

I think it would be very difficult to do an experiment of this sort in practice, and there would inevitably be loopholes, i.e., ad-hoc alternate explanations of the result. But in a thought-experiment, you can close loopholes by fiat and assume quantum mechanics to be true, and the prediction of quantum mechanics is unambiguously that the uncertainty principle applies when there isn't an interaction just as when there is.