Optimize Concept Set Returns More Concepts Than Original Concept Set

I'm on ATLAS 2.15.0

I just had a bug I've never seen before; I ran Optimize and it un-optimized my CS:

<img width="733" height="275" alt="Image" src="https://github.com/user-attachments/assets/b5a1e32d-450b-404d-a71c-40a37f681ed2" />