Chickens standing on a slab DO NOT die from lava above

In this version of my Chicken Farm eggs are shot out of a dispenser onto a slab and lava is dispensed above to cook them when they grow.

https://youtu.be/a7Gy9FVXv-k

However, on version 1.2.13 on XBOX 1 the chickens are not getting cooked when they grow. This only affects baby chicks that grow up normally and does not affect adult chickens that are spawned in. Also, this bug is not related to the issue of chickens taking damage from eggs being shot out of a dispenser.