Likewise you could argue that the coastline problem is limited to at most the Planck length. Most models of stock movement are modeled mathematically with Brow

Likewise you could argue that the coastline problem is limited to at most the Planck length. Most models of stock movement are modeled mathematically with Brownian motion which is by definition a continuous time process. You can even more trivially show that stocks are non-differentiable if you want to argue that they are fundamentally discrete time processes, in which, by definition, they are not continuous, differentiable functions. But the argument of about "what does continuous even mean when we talk about physical systems" is another and older argument altogether.