Holding down the Fire button in this way increases the scope magnification from 2x to 10x.
The shot is fired immediately on release. This does NOT cause the Krysae to do additional damage.
The Krysae has a feature where shots can be "held" by holding the fire button down, similar to the "charging" feature of weapons like the Venom Shotgun or the Graal Spike Thrower.
The Krysae is noticeably stronger in single-player compared to its multiplayer counterpart.