Hi,
No, you don’t have to install your Cubase 6.5 to the new system. It’s just about the license check. At the moment, you will activate the upgrade license in the eLCC application, the eLCC application will test, if there is Cubase 6.5 license on the USB-elicenser. If there is, the license will be upgraded. Then you can install and start Cubase 11.