What is their new interpretation of paladin smite and where might I read about it?
There's no "new interpretation" of smite per se, just that mechanics similar to paladin's smite have been implemented in BG3 differently than 5e.
In BG3, you choose to sneak attack and perform maneuvers
before you make an attack role, via a dedicated icon that includes the attack.
In 5e, you can choose to do some maneuvers (e.g., Pushing attack) or add your sneak attack dice
after you hit. Specifically, after you know that you've hit so you don't waste the resource on a miss.
Thus, if BG3's trend continues for smite, there will be a dedicated "Smite" icon in your hotbar that costs an action to use. You won't be able to choose to smite only after a successful hit or smite only on critical hits.