The bug

At the moment, mobs don't save attributes if they turn into other mobs.

How to reproduce:
1)Enter a command:
/summon minecraft:hoglin ~ ~1 ~ {CustomName:"\"Говночист\"",CustomNameVisible:1,Attributes:[{Name:"generic.movement_speed",Base:5.1f}]}
2)Wait for the transformation of hoglin into zoglin
Waiting:Zoglin has the same value of the generic.movement_speed " attribute, Base:5.1f ✔
In the fact: Zoglin has the standard generic.movement_speed attribute, not the set one❌
Note that zoglin saves the name, but not the attribute.
Works with piglin turning to zombified piglins, villagers to witch, turning villagers into zombies and Vice versa.