Well, if you can't see how having an extra name on a list helps to achieves making an award to a deserving writer, or think it conflicts with that aim, then I cannot help you.
And if you've not observed some of the commentary in the past from people who are concerned about the commitment involved, then I cannot help you either.
Surely, adding a new name will do nothing to ameliorate the commitment. It will actually increase the need/pressure to read more instead of truly assess the impact of a writer in one's life. If a writer shows up again on the list it's a wonderful opportunity to read more works by that same author and/or to reread some others.
I sincerely think this is a false issue becuase even if one writer shows up on the list again, you will still have 2 new ones to consider from. The need for freshness should not be the point of the award as it does not serve a commercial endeavour of any kind.
Plus some writers have, sadly, passed away (Marias) which already "creates space" for new names.
As I have mentioned before, it is actually punishing for a writer to suddenly have to compete with 3 and not 2 others just because he didn't win the first time.
Moreover, are we passing up truly deserving writers (examples are plenty) just because of the artifical need for "freshness"?
If I was a writer and this criteria was presented to me, I would actually wihdraw from competition because it is disrepectful towards one's work.
Slow and steady is, in this case, better than fast in furious. I think.