Every heard about floating point numbers? Or the Pentium bug? Things may be deterministic, but they are not perfect.
"AI has (among other things) a random number generator at its core. It will produce different outputs, randomly, for the same input. Certainly not "perfection"."
That wrong on so many levels. First you use the term AI, which is a huge field in which many thing have nothing to do with random numbers at all. Let' be fair and put LLM there. Then you assume a LLM must be sampled stochastically, which is one method but not the only one (and in many tasks one uses low to zero temperature). And finally you assume that you sample with non-zero temperature and do not fix the seed even though you desire repeatable output.
A neural network is *literally* a function. It maps one large vector through matrix multiplications to another large vector. If you want (and one does it because one wants it) a random component to get diversity in the outputs, *you* are adding the randomness intentionally.