Not just the way it's arbitrarily hard from an engineering perspective to design an experiment to disprove string theory. It is theoretically impossible, the way it's impossible to distinguish between Copenhagen and many worlds.
No, you actually can. The authors of this article discuss the issue more in their longer paper here: https://arxiv.org/abs/1912.06462
The idea is that superdeterminstic theories are deterministic, while quantum mechanical measurements are random, so you should be able to set up an experiment where QM predicts you would just get random results, but actually you get the same result each time.
There are many classical physics experiments you could do where you understand all the physics and formulas to excruciating detail and you control every variable but you still can't get the same results everytime. Things like throwing dice, as mentioned in the article, or the chaos generated by flowing fluids. Given that any superdeterministic mechanisms would be even even more complex and weird and unknown it seems impossible to disprove. Any failed experiment could be excused by saying that there are more unknown uncontroled variables.
Well, the determinist would argue, that, if you cannot predict the result reliably every time, you do not actually know all the variables, even if you think you do.
That's the whole point right? The hope is to figure out what the hidden variables were, to make better predictions than quantum mechanics could. To un-hide them, as it were.
Not just the way it's arbitrarily hard from an engineering perspective to design an experiment to disprove string theory. It is theoretically impossible, the way it's impossible to distinguish between Copenhagen and many worlds.