As I understand it, because we're using a federated system the only way to keep track of votes at all is if one instance tells another "such and such a user up voted this post". Whether or not a user interface surfaces that information so mods or admins see it is a separate question, but the data is there, so a safe assumption that whatever you vote on will be accessible to others.
That might be a setting specific to that instance. With other kbin instances it is possible to see reduces (or at least you have been able to do so in the past).
Maybe there's been a recent update to all kbin instances so that the reduces tab is no longer clickable?
I'm fairly certain that I checked it out on Kbin.Social about a month or two back and it still worked then, but Kbin.Social is currently down for maintenance, so I'm not sure.