In case we have a deleted page, the page is instantiated with only a tombstone on chain. When we reconcile that page, we allocate an external update and select that update to write to disk (WT-5302). Why we just append the update after the tombstone so that we can get rid of the ext flag and some other checks? The append operation is cheap and it has no harm I think. If we decide to evict this page, the chain is discarded. If we keep it in memory, it is still correct. There may be other things that prevents us from doing this.