Originally we designed the config.rangeDeletions collection to have a 'pending' boolean flag whose presence indicated that the range was not yet ready to delete, and doing an $unset operation on that flag would trigger range deletions. After spending a little time with that implementation it seems like it would make more sense to just have a non-optional flag 'readyToDelete' which is either true or false, and setting the value to true is what triggers deletion.

We will do this ticket in a final pass after other functionality is in, since this is really just cleanup work.