It’s a pretty different situation under closer examination. The DnD developers are ex-Nexon employees and they (allegedly) pitched the idea internally before deciding to leave and take the idea with them.

Nexon thought that they had a legal leg to stand on because of how IP laws work (i.e.: employee ideas on company time are company IP). Perhaps more importantly; they probably felt a need to retaliate in order to send a message to other employees who might want to try something similar.

Palworld, on the other hand, is made by a team with no ties whatsoever to GameFreak. If Pokemon were a younger franchise they might possibly have a patent case of some kind, but even the 3D games go back almost 24 years now.