They probably use WCID, which is a mechanism for devices to tell Windows that they are compatible with the generic WinUSB driver. Zadig is useful for older versions of windows, non-WCID devices, and when you want to override that auto-specified driver.
They mentioned below that they have their own devices they can control. As I understand it, for those kinds of IoT usecases the workflow is easier because, instead of overriding the driver defined by the OS, you can define WebUSB-compatible descriptor that will "just work" across all platforms.