Undead mobs such as Zombified Piglins and Zombies will not consistently attack Turtle eggs. I tested this by spawning the mob at a 1 block radius and 75% of the time they would walk away. I left them for at least 10 seconds and the majority of the time they would not pathfind even with nothing else to pathfind to.
Likely intended, it's not #1 priority in their AI at the moment.