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: Obligatory RIP my inbox.
…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.