Our Gemara on Amud Beis tries to figure out how to properly allocate and position the number of graves described in the Mishna, and reconcile it within the stated dimensions of this space. One idea that was considered was that some bodies were buried standing up. The Gemara firmly rejects this as absurd, since this would be a disgraceful manner to lay a corpse. The Gemara declares:

This is like a burial of donkeys and is disrespectful.

This statement also can be interpreted allegorically. A standing position represents standing still. Yechezkel (1:7) describes angels as having legs that are straight, with no joints. This implies they never need to sit or bend down. Toldos Yaakov Yosef (Bo 73) interprets this to mean that, unlike humans who must constantly be working on growth, angels are static and do not need to develop abilities - they are what they are. If so, the message is as follows: One who is buried standing up, i.e., someone who stagnated in life and didn’t grow, is as if he is a donkey.

Related to this we find a derush from Eretz Chemda (Vayechi 6:1) which suggests that Esau wanted to be squeezed into the Machpeila burial cave by being interred standing up. Of course, Esau who did not express any higher aspirations than physical gratification, would be fine if he were buried standing up, representing no growth. And as a final thought, the Torah ethic not only expects growth, but movement and growth. The verse states (Devarim 6:7-9):: 

Impress them upon your children. Recite them when you stay at home and when you are away, when you lie down and when you get up…inscribe them on the doorposts of your house and on your gates.

Notably, Rabbenu Tam’s (Tosafos Menachos 3a) offers an objection to Rash’s opinion that the Mezuzah should be affixed vertically based on our Gemara’s burial protocols, which indicate that a vertical position is not respectful. If we apply our idea, which equates standing with spiritual stagnation, here too we can interpret Rabbenu Tam’s idea allegorically: The mindfulness of Torah and its teachings that must pervade our home, which are symbolically expressed via the Mezuzah on the doorpost, must be a include a growth mindset and not stuck in one place.