I think it does work through the lens, in a way, but it doesn't take a strobe command directly from the camera, like a wired TTL strobe. The strobe must pre-flash when the sensor sees the camera pre-flash, so the camera 'sees' the effect of both its own light and the light from the strobe during the pre-flash evaluation that it uses to set its exposure flash duration. Then when the exposure flash happens, the strobe sensor watches that and quenches when the camera flash quenches. Thus a TTL-like result.
This approach is used by the external Weikamp TTL adapters that have been around for years, from what I understand. When I contacted Weikamp a few years ago, this is how they explained the TTL capability of their setup.