Questions on Third Law of Thermodynamics

Third Law of Thermodynamics reads:


**at absolute zero , the entropy of a perfectly crystalline substance is zero.**


(<https://simple.wikipedia.org/wiki/Third_law_of_thermodynamics>)


And considering the Boltzmann equation:


**$S=k\ln\Omega$**


then we can infer that at absolute zero, a perfectly crystalline substance can be in merely one state. But is that true?


At absolute zero, a perfectly crystalline diamond containing a mixture of C-12 and C-13 is able to be in different states with different patterns of isotope. And a perfectly crystalline hydrogen containing a mixture of ortho-hydrogen and para-hydrogen is able to be in different states with different patterns of nuclear spin. Then can we conclude that the entropy of the diamond or hydrogen is greater than zero?


Since the dimension and realm of microcosmic structure has been expanded continually, there might be more isomerism forms other than isotope and nuclear spin isomerism to be revealed and we are not sure where is, or even whether there is, the ultimate of the microcosmic world. And how can we convince ourselves that all the isomerism of all dimension and in all forms is going to disappear when reaching absolute zero?


What's more, we don't need an absolute enthalpy but rather a relative one, while we indeed need an absolute entropy in physical chemistry as an essential part, so there should be an absolute origin for entropy and thus I shall not doubt the universally recognized Third Law, so what's wrong?
Does the word perfectly crystalline has in definition excluded all the forms of isomerism? Or are all the isomerism phenomena going to disappear when reaching absolute zero? Or is it that we simply omit the entropy produced by isomerism?(But, for example, the molar entropy produced by 50:50 isotope is $k\ln C ^{\frac{N\_A}{2}}\_{N\_A}$ and thus not neglectable. )


