Nit: no ML is deterministic in any way. Anything that is Generative AI is ML. This fact is literally built into the algorithms at the mathematical level.

First, they all add a source of randomness, and second deterministic according to the users model. A pseudo-random number generator is also deterministic in the technical sense, but for the user it isn't.

When the user can't reason about it, it isn't deterministic to them.