I have experienced both sims culling and relationship culling.
Sims culling deleted half of my towns. ruined my stories. Many of my sims lost their love interests, children, parents, siblings, friends, enemies. It was a true disaster.
Relationship culling screwed all relationships in my game and also contradicts with the purpose of Get Together EP. To me now it feels as if the developers made this EP specifically to justify the introduction of the new relationship culling.
Next will be pets culling, objects culling, skills culling.
The future of this game is very uncertain.