Quick Question About Shabbos, Yom Kippur and Avinu Malkeinu

Normally, on Yom Kippur, we say Avinu Malkeinu (Our Father, Our King) after each of the services. This year, however, because Yom Kippur comes out on Shabbos, it will be omitted (as the prayer is always omitted on Shabbos). Nonetheless, it *will* be recited following the last service, Neilah, at the close of the day.

My question, very simply, is why?

I came up with two hypotheses:

1. Since it is after shkiah (sunset) and it is only a safek (doubt) as to whether it is really Shabbos or not (depending on whether the day begins at shkiah or tzais hakochavim [when the stars appear]), we say it.

2. Neilah, being the last prayer of the day, is meant to end on a spiritual and emotional high note, and so the prayer is recited anyway, *despite* the fact that it is Shabbos.

Of course, the real answer could be a combination of these, or neither of the above.

Anyone have any thoughts?

The Wolf