Was Our Infant Lord in the scene?  If not, it's non uncommon to set up the entire scene absent Our Lord beforehand.

There's plenty to criticize the SSPX about, vis-a-vis their movement toward Modernism, but this is much ado about very little.  People should take the beam out of their own eye before criticizing the splinters in those of their neighbor.

There's no Church law they're violating.  If people want to set up the ENTIRE manger in their home, for instance, starting in April, to aid in meditating upon the scene, what's that to anyone else?

We need to make sure during Advent that we are prayerful, do penance and alms like St Nick.