What do the final paragraphs of the story, the entering and examining of the closed room after Miss Emily's burial, contribute to the story as a whole, besides a surprise?

We not only get a surprise, we learn how truly "sick" Emily really was. How many people would sleep with a corpse? A little touch of gruesome morbidity.

"For a long while we just stood there, looking down at the profound and fleshless grin. The body had apparently once lain in the attitude of an embrace, but now the long sleep that outlasts love, that conquers even the grimace of love, had cuckolded him. What was left of him, rotted beneath what was left of the nightshirt, had become inextricable from the bed in which he lay; and upon him and upon the pillow beside him lay that even coating of the patient and biding dust.

Then we noticed that in the second pillow was the indentation of a head. One of us lifted something from it, and leaning forward, that faint and invisible dust dry and acrid in the nostrils, we saw a long strand of iron-gray hair."