Exactly. Anything that's ever been public on the internet is never really gone anyways, and it's unsafe to assume so. This is similar to publishing a website or a blog post. Plus, from a practical (non-opsec) point of view, you can delete items (posts, likes, reposts, etc.) on ATProto, and those items will disappear from whatever ATProto app you are using - usually even live. You need to dive into the protocol layer to still see deleted items.