Your last sentence is not very clear to me. "But it only does this as long as no index updates are necessary.". Do you mean to say it does only for HOT updates

Your last sentence is not very clear to me. "But it only does this as long as no index updates are necessary.". Do you mean to say it does only for HOT updates? If so, I don't think that is the case, it can do it during a scan of the heap.