That is the Warcraft explanation for werewolves Worgen being affected by moon light - it being Elune’s gaze - which was a bigger factor back in Classic when the Pyrewood Village NPCs would change from Human to Worgen at night (except one Forsaken Worgen that stayed Worgen day and night).
The idea that Elune would shine down her light on the Night Elves would likely not encourage the Worgen to temper their rage for Gilneas, and if anything it might make the Worgen even more resentful instead. So if anything, Malfurion’s survival could potentially have pushed the Gilneans even further away, or at least Sylvanas might have known this if she learned about the origin of the Worgen curse when she worked with Alpha Prime back on her attack on Gilneas.
Tyrande initiating the Night Warrior ritual, however, shifts Elune from light to darkness, blocking out light on Darkshore, not shining her light down to temper vengence, instead encouraging it, and in that darkness the Worgen - at least the ones that join Tyrande in the Horde quest “The Dead of Night” and get enhanced by the Night Warrior ritual, too - unify even more with the Night Elves.
Which, granted, is exactly what Sylvanas hoped for:
- Anduin Wrynn would have lashed out in a final, desperate war, looking for a miracle, because only a miracle would save them.
But then Alleria and Jaina show up to be that “miracle” (not Malfurion’s survival like Sylvanas was ranting in her mind about in that monologue). Sylvanas really should stop betting against “miracles.” It has consistently not been paying off for her.