To save space I wont quote you Mura.
Flip reverse the situation. Rushing someone with a SO when they have a Gnasher. You can't approach from the stairs, they'll down you before you even get in range, so your options are die or run. You can't approach from the bottom, you'll be downed before you can get close, your options are run or be killed.
It seems that, for being a "broken" weapon, it is actually the crap weapon to choose when compared to the Gnasher. No matter how fast you travel you'll get shot, and the fastest you can move is by sliding into cover towards the corner. You'll have already been shot once, due to having to advance in an area with no cover, and the second shot will down you or gib you as you'll now be within Gnasher gib range and you can't slide into cover and shoot at the same time.
As you can see that situation has nothing to do with the SO, it's the area that person is controlling, the smart decision to use the Gnasher as it completely shuts down the approach of the SO and you don't have to retreat after 1 shot.