User blog comment:Crimson and Darkness/Volume 25 discussion blog/@comment-73.57.25.92-20180405214635/@comment-24595619-20180407004124

You can't really say that Saji's Sacred Gear won't become a Longinus not since you aren't the author. Azazel mentions several times that Longinus are just sacred gears, which contains a bunch of different abilities.

Saji possess all of the Vritra Sacred Gears whoses abilities affected Loki after his arrival on the battlefield and could counter the divine flames Longinus Incinerate Anthem. So you can't say that his progession into gaining a Longinus impossible. It all depends on what the user's development and their desire to grow.

Vritira couldn't be classified as a Longinus because he had his soul split into four pieces, which were then seal in four different sacred gears, which again Saji currently possesses.