Answer
Actually, the magisterium’s language isn’t that specific. Although the Aristotelian distinction between substance and accidents has been used by Catholic theologians, the Council of Trent opted for a broader distinction of substance and species, which does not necessarily imply any particular theory about the nature of the relationship (whether "accidental" or otherwise) between what a thing is and its sensible attributes. All this necessarily pins down is that the eucharistic elements continue to manifest all the physical properties of bread and wine, but what they are has been completely changed.
