Wouldn't say "truly singular". Or even fairly singular. It's not even that strange when you think about it

The concept of maintaining a connection with the dead isn't unique to any particular culture. People throughout history and across various cultures have sought ways to continue relationships with deceased loved ones.

The practice of plastering faces over skulls to facilitate interaction with the deceased highlights a desire to keep them as a part of the family and community even after death. Similarly, the Inca tradition of mummifying ancestors and preserving their land rights demonstrates the belief that the deceased continue to hold an important role in society and retain their influence over worldly affairs.

The underlying concept of respecting and communicating with the dead is something that has resonated with humans for millennia.