You're absolutely right, the series is an exercise in quiet tension. It doesn't need jump scares or grotesque monsters; the true horror lies in the atmosphere, where the ordinary feels subtly twisted. That stillness you mention, where shadows stretch and conversations hang in suspense, is what keeps you glued and suspicious of everything.
I was fascinated by how they handle the characters. There's no hysteria. Just a very human and restrained reaction to the irrational. The protagonist trying to apply logic to something that constantly challenges it is brilliant. It's a gem of slow-motion narrative and observation!