"I am not allowed to leave the cabbage and lion alone together, and I am not allowed to leave the lion and goat alone together."
It says nothing about the cabbage and the goat. It would not be unreasonable to infer that you aren't allowed to leave the cabbage and the goat together, based on how goats normally behave.
Of course, that makes the puzzle unsolvable, which is why humans will catch onto it pretty fast.