You must have confused CYVR for MSFS ( called "Vancouver V2" ) with the FSX version so, when you clicked Install, it told you that Install feature ( not the scenery ) is not available for FSX/P3D, that's because the FSX/P3D products have their own installers that can be always downloaded freely.
However, while you can't install an FSX/P3D scenery with the FSDT Installer, you can use it to Update it.
The products for MSFS, instead, are both Installed AND Update from the FSDT Installer.