CompSci theories are essentially mathematical proofs. You create a proof of something, then you build it to test it, to make sure your math is actually correct, and that the theory works in implementation.

Proof of correctness doesn't rely on having a large cohort of test subjects undergoing an experimental trial of some sort, and then interpreting the results with statistical models, distributions, p-values, etc.

I don't know psychology in depth, but if there are similar kinds proofs without requiring statistical analysis of a large experimental cohort, then I don't think Taleb's criticisms are aimed at those either.

It's the fundamental problem of knowledge - can truth be known via logic and reason, or via empiricism and observation? The answer to both is, sometimes, but with caveats.

Peter Norvig also wrote a good take on all the ways studies using experimental cohorts can go wrong: https://norvig.com/experiment-design.html