Applications which use the device path to differentiate cameras stumble since every registered Unity Video Capture instance uses the same device id. OBS has no problems with it, but for example Zoom shows all cameras but only allows to select the first one. Skype only shows the first one.

Quoting from the Microsoft docs:

The "DevicePath" property is not a human-readable string, but is guaranteed to be unique for each video capture device on the system. You can use this property to distinguish between two or more instances of the same model of device.

To be honest though, I'm not sure if this hack is needed anymore. The virtual camera from OBS doesn't have a device path and works in all apps incl Skype. Maybe it got fixed at some point in Windows? The forum thread referenced in the code is 9 years old.