I'm not entirely sure about that. More members, sure - more fair, I don't know.

For instance, let's take SpamBuster category and assume it is objectively ranked by most successful (true positives) spam reports.
Assume it is 2022; UserA reported 1000 posts in the year, and UserB (ranked second) reported 100 posts, everyone else under 100 posts. UserA wins the category and takes home first place.
Let's say in 2023, the numbers are exactly the same. UserA again reported 1000 posts and the next best user only reported 100. So UserA did the exact same job, and everyone else performed exactly the same, too. Now, only because this is the second year, UserA will have to share their prize, even though nothing changed.

By knowing about this rule, UserA may be discouraged from reporting 1000 posts again, since they could just as well aim for second (or lower) spot instead with much less work involved.
I'm all about encouraging instead of discouraging, so therefore I lean against such a solution.