No I think the backstab bonus damage is only for the rogue. But still, the advantage is there for everyone and makes it so easier to hit the target if you are behind them even though you were in front of them a few seconds earlier, like the enemy has some kind of fish memory and forgot you were there.
Yeah, sometimes folks lump sneak attack and backstab together because they've been used to mean similar things in other games. In BG3: Sneak Attack (damage) = Rogue. "Backstab" (advantage to hit) = Everyone.