Typing is not a noisy source. It should be reliable and deterministic.
Protecting an agent from fairly obvious attacks should also be deterministic.
Real world is probabilistic in practical / metrological, if not fundamental sense, and separation between data and execution does not exist. Our reality does not support such separation.
> a probabilistic/stochastic word generator on top of deterministic circuits instead at 10 magnitude worse efficiency
It's 10 magnitude better efficiency end-to-end, if you factor in design time you'd have to spend to get your "deterministic circuits" (which really aren't, we just paper over it) into shape so they deterministically solve a specific problem, for each problem you want to solve - where with the "stochastic word generator", you just need to change the text prompt.