If the L5Y thing were happening longer into a run, it likely wouldn't be a problem- Zegler would take the two weeks off. But the scheduling for this would require her absence during rehearsals, tech, or early in performance, which is much harder to manage. Zegler missing half of previews, for instance, would kill sales from the jump and then require additional rehearsal time to get her back into it.
"...everyone finally shut up, and the audience could enjoy the beginning of the Anatevka Pogram in peace."