Thank you for reporting a bug to Unity.
We have reviewed the issue carefully, and in this case, the team is unable to prioritize fixing this bug. The issue itself is tied to the fact that the triangle x triangle check between terrain and triangle mesh would require some changes which have the potential to impact/ripple across different use-cases. We will open a ticket internally to keep track of this issue and will investigate what changes can be done down the line as we stabilize the PhysX <-> GameObjects integration.
Cheers,
AlexRvn
Today we will be closing this case. Thank you again for taking the time to report this issue, and please let us know if there is anything else that changes the impact or severity of this issue.