Priests where always female back then, hence the name sisterhood of Elune.
That was changed with world of warcraft:
The Sisters are a major and active night elven political faction, and fulfil the role of magistrates, officials, and others for the night elven government. The highest-ranking of the Sisters are privy to the government's most important secrets, such as the original condition of Malfurion Stormrage and the power struggle that erupted between Tyrande Whisperwind and Fandral Staghelm.
The Sisterhood of Elune is the highest echelon of the priesthood that serves the goddess of the moon, Elune. The Sisterhood has remained exclusively female up until recent times. This is largely because of a common belief that the deepest mysteries of Elune can only be comprehended by women. Although the vast majority of Elune's priesthood is still comprised of night elven women, the order has come to accept Kaldorei males into its ranks as well.
https://wow.gamepedia.com/Sisterhood_of_Elune
So there were no male priests before the time around when world of warcraft started.
But even with that I think you could argue that this ritual could be done by a male warrior of the night elfs... it seems more likely that the sisterhood acquired the understanding and knowledge about this ritual and since the priestress ware often warriors themselves, they probably tried it themselves.