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.
Wouldn’t it be easy to lie though? Instance B could report 1000 upvotes to Instance C and Instance C would have no way of verifying that. An instance could boost its own numbers pretty easily, pushing agendas to the front page.
The transparency allows for accountability. It would be pretty easy to detect an instance making up user upvotes versus a “just trust this number” system.