Mobs Suspended by lead mid-air gain velocity

What I did: Suspended a mob on a lead to a fence post mid-air , then i broke the lead and expected the animal to run off

What happened: the mob fell one block and instantly died

Why? (My inference): While the mob is suspended the game mechanics increase its velocity as it thinks it is perpetually falling, once the lead is broken the animal hits the ground at a massive velocity and dies.