But it's quite commun, you got the same with LUXAIR, THAI Smiles, Andalujet, etc (all benefits for Miles and More members, no benefits for gold, even priority boarding and checkin).
You got the benefits if you are gold with the mother program but not with star alliance as those airlines are not in the alliance, sounds logical but of course should be nice that star alliance ask the airlines to include those airlines as "member partners" and bring the benefits for star alliance members.