> In Physics, entropy is a property of a bit of matter, it is not related to the observer or their knowledge. We can measure the enthalpy change of a material sample and work out its entropy without knowing a thing about its structure.

Enthalpy is also dependent on your choice of state variables, which is in turn dictated by which observables you want to make predictions about: whether two microstates are distinguishable, and thus whether the part of the same macrostate, depends on the tools you have for distinguishing them.