i'm not sure. some sort of conscious acknowledgement that they are An Item or that things are Definitely Serious maybe. the thing about cloud and aerith's could-have-been-relationship is the game very deliberately and cruelly subverts the player's expectations. the player plays the first disc of the game expecting them to become the game's Official Couple and then this is made completely and finally impossible when she gets stabbed through the heart. the rest of the game, if i am not misremembering, even goes so far as to mock the player's expectations by still selling items she could use if she were alive but, of course, she will never use them because she is dead. the entire romance setup between cloud and aerith is meant to be a suggestion of potential that will never be realised because of her cruel murder, which just twists the knife of her sacrifice in further. there was potential for A Relationship there, but what happened did not progress enough to qualify as one.