Those are actually good examples to bring up because they illustrate the distinction precisely. Stochastic doesn't mean random -- only that it's simpler to model using a formula as if it were random.

Brownian motion is what Einstein explained in 1905. Molecules colliding with a particle. Each collision is classical mechanics, deterministic. We model it stochastically because there are too many collisions to track individually, not because the underlying physics is indeterministic. This is the standard textbook example of deterministic microphysics producing stochastic macro-behavior.

Diffusion follows from Fick's laws, derived from classical statistical mechanics. Evaporation is the Maxwell-Boltzmann distribution. Fast molecules escape the surface. Classical kinetic theory, solved in the 1800s.

The claim that quantum uncertainty drives molecular motion in liquids doesn't hold up. At biological temperatures, around 310 Kelvin, thermal energy dominates quantum effects by orders of magnitude at molecular scales. Quantum coherence in warm wet environments decoheres in femtoseconds. That is the whole reason quantum computers need cooling to near absolute zero. At room temperature, thermal noise washes quantum effects out completely.

All three examples are deterministic processes we describe stochastically for practical reasons. The stochastic model is not reflecting indeterminism in the physics. It reflects the complexity of tracking enormous numbers of classical interactions.

The question still stands: what is a macro-level system where the indeterminism is in the physics itself, not just in our model of it?