Edit: obligatory explanation (thanks mods for squaring me away)…
What you see via the UI isn’t “all that exists”. Unlike Reddit, where everything is a black box, there are a lot more eyeballs who can see “under the hood”. Any instance admin, proper or rogue, gets a ton of information that users won’t normally see. The attached example demonstrates that while users will only see upvote/downvote tallies, admins can see who actually performed those actions.
Edit: To clarify, not just YOUR instance admin gets this info. This is ANY instance admin across the Fediverse.
…or just ask any kbin user, we can see up and downvotes through the UI. Upvotes are federated, we see everything. Downvotes - more complicated - we won’t get the full picture for a post hosted on Lemmy, but we still see downvotes by kbin users.