As @Gel214 said, challenge scaling exist in PNP 5e too, the DM is constantly adapting the CR of the enemies to match the power of the party, or the game will lose interest for the players, and combat became too one-sided.
That said if it´s made like in Bethesda videogames It can be frustrating, just as the others in this thread said. In most story-driven RPG you have the scaling because they calculate the max level you will have when reaching certain point in the story and plan the encounters accordingly, something that is not feasible in sandbox-y games like Skyrim or RDR. I assume that would not be the case in BG3
