alt Hacker NewsIt's true you can. Just as you can say that you can enumerate all memory states in a real computer so it can be modelled as a finite state machine. These asymptotic models aren't real (our world as we experience it is finite and bounded) and exist as models from which to gain insights which we can transfer back. I love this argument BTW a classic that usually comes up in these discussions.
Asymptotic models are not a statement of how long it will take; they are classes of functions modeling the relationship between some performance outcome (run time most often, but sometimes memory or other things) and data coming in. These mappings from input to performance characteristics are not conditioned on physical limitations but are rather abstract tools for measuring that relationship.