Flechettes aren't released until the round is almost to the target. Notice the part about the time fuse in your quote. Otherwise, accuracy would be terrible.

everyone says any new suggestion is OP but their own. this one seems like it makes sense though. he's probably not thinking shotgun as the damage, but as how it hits people, spreading the damage around. right?

...putting an inert round downrange in excess of 2,500m/s...

Shouldn't these guns make a sonic boom when fired?

My guess would be that the round doesn't expand until its close to the target because of some sort of proximity fuze to maximize damage.

They say it's a timed fuse. It's logical to assume it's a timer that's set when firing based on range to target (the gun tracks that, remember?). "It is intended for use in direct fire against enemy troops" tells me it's designed to hit a single target, not a "spread" like OP is suggesting, which would be more of an indirect fire weapon.

Basically, just before hitting the target, the projectile should be splitting, spreading its impact across a wider area on the target rather than a single impact point. This would have the effect of negating any defensive countermeasures that reinforce the predicted point of impact, by spreading the damage around that target location.

EDIT: Also, "snipper riffles" instead of "sniper rifles" - really?

They say it's a timed fuse. It's logical to assume it's a timer that's set when firing based on range to target (the gun tracks that, remember?). "It is intended for use in direct fire against enemy troops" tells me it's designed to hit a single target, not a "spread" like OP is suggesting, which would be more of an indirect fire weapon.

Basically, just before hitting the target, the projectile should be splitting, spreading its impact across a wider area on the target rather than a single impact point. This would have the effect of negating any defensive countermeasures that reinforce the predicted point of impact, by spreading the damage around that target location.

EDIT: Also, "snipper riffles" instead of "sniper rifles" - really?

Another EDIT: Also, it's an "inert" projectile, which means no internal explosives, which means no blast to scatter the flechettes, which in turn should result in a VERY tight spread, and probably at the very least, the appearance of only a single impact point with a close-range separation, if not an actual singular hole because of the tearing effects of the multiple closely-packed impact points.

You fire a shotgun into the side of a building from about 5cm away, you'll probably only have one hole in the wall.

The sound you here when the rifle fires is the sonic boom mostly. Even a regular rifle, the rifle crack is the sonic boom of the bullet, and why silenced weapons use subsonic ammo.

The beehive flechette in description is singular, so it shots only one. The U.S. looked at replacing AR with needle guns firing flechettes in late 1980's, they worked but not well enough to justify replacing M-16.

It may be referred to as beehive since it is the size of the flechette used in a artillery weapon in multiples? A big HAV shotgun turret would be interesting for clearing bunched infantry.

Shotgun sniper is ... OP

This is a sci-fi game.
It does not have to obey the laws of real guns.

The only law it must obey is The Law Of Cool.