To expand: the concern from some instance admins (who?) is that people could have e.g. racist or otherwise problematic posts deep in their history, and those would be 'grandparented in' with little scrutiny.
I don't quite get 1. why the normal flow of people eventually seeing those and reporting them is not good enough and 2. why it is suddenly OK for good actors not to be able to perform basic reasonable actions in systems because bad actors might abuse them.