Questiions on the Simbang Gabi take 2

As I was praying the Office of Readings for the 4th Sunday of Advent (Novus Ordo), it just dawned on me that this particular Sunday does not have its own Office of Readings. Rather, the rubrics will direct you: Verse, readings and responsories from the office of the day. Also, the antiphon for the Magnificat is also taken from the office of the day. The Ordo for the Philippines directs that at the Simbang Gabi on the 4th Sunday of Advent, the priest wears white and the Gloria is sung. But the Readings and Texts for prayers will be of the 4th Sunday of Advent. Apparently, this is due to the fact that in nothing takes precedence over a Sunday of Advent. But my contention is that this is not so as indicated in the indult for the Rorate Caeli Mass during the Simbang Gabi. See sense of the sacred: Questions on the Simbang Gabi

If the Divine Office on the 4th Sunday of Advent gives way to the readings of the Office of the day, why can't the same principle be applied to the readings of Simbang Gabi?