Rashi explains that Esau knew how to trap with his mouth, to deceive. He asked his father how to tithe salt and straw, things which don t require tithing. His father assumed from these questions that he was very pious. All things are not created equal. Some things are of the essence, others are subordinate.
Every palace has an entrance hall.
No one would confuse the importance of the entrance hall with the palace itself. The palace is the essence. The entrance hall has importance only because it is the only way into the palace. This world is merely an entrance hall to a great palace of light the world to come. The world to come is the essence.