The Starks cannot seem to follow rules. Jon had issues with rules and so does Arya. Bran continues the ignoble family trait with what he does to poor Hodor and the cannibalism. Soon he will start craving blood.
The red material in the porridge was not Jojen's but it is the accumulated human blood from the trees. The sap is the blood of all the people who were sacrificed to the trees. Bran ate blood but it was not Jojen's. Not yet anyway.