How can you tell if posts are actually being removed?

Start with specific examples, not a general impression. Record the post’s date, account, and wording, then check whether the same item is still available directly or appears in a reliable archive. A missing search result by itself does not show that a post was deleted.

There are several ordinary explanations for something becoming hard to find: search ranking changes, an account changing its own posts, a visibility limit, or a moderation decision. Without a dated record or a clear notice, it is tough to tell which happened, let alone establish a wider pattern.

I’d be cautious about drawing a conclusion from a handful of examples. Compare a defined set of posts over time, and keep track of what you searched for and when. If there’s no consistent record, it may be better to call it an unverified claim.