Ah shoot, you're right this wouldn't be what I'm thinking.

I was thinking of "GC Nepotism" [1]. That's the case where an object in old gen pointing to an object in new gen will automatically promote that new gen object into old gen. This can be particularly problematic with graph structures.

[1] https://psy-lob-saw.blogspot.com/2016/03/gc-nepotism-and-lin...