This is an expected behavior. When the CYUSB3 driver is installed on the PC, the system remembers the driver information. The CYUSB3.INF file has the VID/PID combinations defined by Cypress. When any of these VID/PID is used in the firmware, the CYUSB3 driver gets automatically loaded. When a VID/PID other than the ones in the CYUSB3.INF file is used, the system does not find a suitable driver and hence displays the device under 'Unknown Devices' section in the device manager. The device then needs to be manually bound to the corresponding driver.
Thank you. the question is perfectly answered.