Hello!
The issue described in this case is occurring as a result of a previous bugfix. During the 6.X cycle Unity's SaP (Sweep and Prune) option in the Project Settings -> Physics -> Settings tab would internally be treated as ABP (Automatic box pruning). ABP performance is far higher for insertions/removals/changes within a physics scene's broad phase. The bug fix I'm referring to simply ensured SaP actual evaluated to eSAP in the PhysX integration code.
Thank you for reaching out and submitting this case!
Cheers,
AlexRvn