I'd be very interested in hearing and explanation and understanding why superdeterminism cannot be tested (it's not clearly obvious to me how that's the case) because if that is the case, it would explain why it was largely unpursued/undeveloped (similar to what someone else in this thread posted--if it's true, it supposeldy offers little useful insight beyond better explaining issues in quantum mechanics by replacing one blackbox of uncertainty with another).

Based on the author's description, much of the issue is that the theory has had little attention and as such, is largely undeveloped (and therefore, isn't going to be developed enough for experimental testing).

What experiment could you run in a superdetermined universe that would distinguish it from a non-superdetermined universe? Vice versa? There's nothing.