User blog comment:B214/Question and Answers 6/@comment-217.115.65.19-20190123111025/@comment-10330822-20190126130153

That is never stated to be the case. What DevilSlayer is saying is that unlike Twilight Healing, which is confirmed to have multiple users, Forbidden Balor View is never stated not to be unique, for all we know there is only 1, and the reason is because a piece of Balor is sealed in it. The reason there is only a piece if because Balor was killed by Lugh, not because he's in other pieces.

That is what he means by Twilight Healing being "rare but not unique". The Forbidden Balor View on the other hand is never stated to have other versions, that was Twilight Healing. We've been treated to so many rare kinds of Sacred Gears like they aren't anything special, because its how the author creates more powerful characters. In realty, if you gathered 1000 reincarnated devils, you'd probably get only a dozen Twilight Healings.