SERVER-91109 made resharding recipient shards that do not own chunks for the collection (currently, this can only be the primary shard) after resharding skip cloning documents and fetching/applying oplog entries for it. It didn't make the recipient shard also skip building the indexes since currently collMod also targets shards that do not own chunks for the collection. SERVER-81033 made it such that the response from the primary shard is ignored if it does not own any chunks. But it is still unclear if it is safe for the primary shard to not have the index for the collection.