Enantiotropic and monotropic polymorphic transitions are distinguished by whether the phase transition is thermodynamically reversible (enantiotropic) or irreversible (monotropic), making this a matter of fundamental thermodynamic definition.
The claim states a standard thermodynamic definition distinguishing enantiotropic and monotropic systems, where enantiotropic transitions are reversible with respect to temperature and pressure, whereas monotropic transitions are irreversible. This is textbook thermodynamic and crystallographic fact defining these phase relationships rather than an empirical hypothesis requiring new citation support.