“We developed a deep neural network that maps the phase and amplitude of WiFi signals to UV coordinates within 24 human regions. The results of the study reveal that our model can estimate the dense pose of multiple subjects, with comparable performance to image-based approaches, by utilizing WiFi signals as the only input.”
You are correct, at best this requires some a priori knowledge of the room. You can kind of do basic motion detection blindly though. They are just measuring the channel response via the 802.11 preambles, so for basic presence detection knowing that the channel response is changing is enough.