Legal content that violates community rules or instance rules but is otherwise harmless like spam, is kept in the modlog just fine. People don’t generally browse the modlogs as you generally can’t interact with the stuff anyway. No upvotes (more likely, tons of downvotes), no commenting. Not much better than going to the internet archive to undelete a post elsewhere.

More extreme content like CSAM usually gets deleted then purged instead, which is a feature that properly goes in and wipes the content permanently.