NBT is removed when zombies/husks convert

Husks or zombies lose almost all of their NBT data when they convert into zombies or drowned mobs respectively.

How to reproduce

1. Use the command /summon husk ~ ~ ~ {DrownedConversionTime:100,Health:1.0} while underwater. Summoning a zombie also works.
2. The husk should have 1 health.
3. Wait 100 game ticks for the husk to convert into a zombie.
4. The zombie will have full health.

This affects almost all NBT. Some of the exceptions that I know of are armor, hand items, and custom names.