Q: The O Antiphons from evening prayer of December 17-23 are repeated at mass as the verses for the gospel acclamation from December 17-24 – except that they don’t line up the same way. Why is that?
A: I wish I knew, but they are different. From December 17-20 they are the same, but on the 21st, the gospel versicle switches to the antiphon from the 23rd. The antiphon from the 22nd appears as the gospel versicle on both the 22nd and the 23rd, and the one from the 21st appears at mass on the 24th. Furthermore, the gospel verses are abbreviated versions of the antiphons from evening prayer.
The antiphons at evening prayer are the traditional ones in the traditional order. Their usage at mass is a post-Vatican II innovation.
If you flip the lectionary over a page to number 201, you’ll see that the seven versicles in their abbreviated form may be used on any of the weekdays from December 17-24. That means that you may use the matching versicles on December 21 and 23 if you wish. Or you may change every single one of them to something else if you wish. I personally like observing the traditional sequence, even at mass.