I find finally at right place in registry thecorrct link which is toward c:\bds\Embaradero\RAD Studio\9.0\bin\bds.exe
Version number of this file is the one you mention, 16.0.4504.48759 whichj also is shown by the compiler help.
Could you have hardcoded the path or is the installer using my admin accounts information? The info is not registered in the current_user key for my admin account as it looks like