I didn't see the American one, but the French one is all about atmosphere imo. I got bored with it. It's hard to write good plots for stuff like this though.
You totally pegged it on atmosphere. But in a strange way -- and here's where the
Twin Peaks parallels come out -- the atmosphere can be good enough where you care less about plot progression, character development, tension and drama, etc. It's weird as a viewer experience ... in fact, when I watched the ending of Season 2 I was kind of taken aback because plot development actually started to happen. And my reaction was like, "Whoah, what was that doing in there?"
Call it a more sophisticated version of Yule Log or, perhaps in Scandinavian terms, slow television. It works on a level of a sense of place and immersing in it without the expectations or trapping of a typical plot-driven television show. But for most people, that pace and that approach may be a bit of a boring turn-off.
Another thing I watched that I really enjoyed in a similar vein was the movie
Under the Skin. The difference was that UtS had Scarlett Johansson oogling and some freakier themes (Scarlett as an alien driving a rape van around Scotland). But what made me enjoy it too was the unconventional aesthetics and pace of the film where it was about the journey and not so much the destination.