Is 'Perhaps the Proximity people thought that they had got round that little problem by giving the same definition for each of the items in the list; but we know that only very rarely are two synonyms bi-unique (which is another way of saying that if A = B, B does not necessarily always equal A), an ineluctable fact of language.' in direct disagreement with the statement 'X and Y are always the exact same thing.'
Perhaps the Proximity people thought that they had got round that little problem by giving the same definition for each of the items in the list; but we know that only very rarely are two synonyms bi-unique (which is another way of saying that if A = B, B does not necessarily always equal A), an ineluctable fact of language.###X and Y are always the exact same thing.