OK, one Redditor has this to say:
"The only magnified weapons are those labeled sniper rifle. The other optic attachments are just misleading with their multipliers... they don't multiply anything. "
So, if we believe this Redditor, then the magnification designations are fake on non-sniper rifles - they don't do anything. So as an example, the Prism Repeating Rifle I found has the "Prism Sight". The description reads:
"2.0x Magnification. Increases weakspot damage and reduces weapon sway."
But, the 2.0x Magnification doesn't work, so the only advantage is the increased weakspot damage and reduced weapon sway. If this is true, it REALLY begs the question why they bothered to include a false magnification factor.