I am sorry for you, but this is obviously a false information from that Lyngsat-page. Even if its possible to use the NDS-cards of Sky-Germany to decode HD-Plus channels these channels are not part of the Sky-Germany package.
But no reason to complain, as I already wrote you can get a HD-Plus subscription via the Billing Center and use it beside your Sky-Germany subscription. The HD-Plus package is charged with 1$/month up to 9,60$/year.