The bigger problem I see is that LH and UA are metal neutral across the atlantic due to the A+ (soon to be A++) joint venture. While inflight service standards won't and are impractical to align, the ground services should be the same. If they want to offer passengers a "metal neutral" experience, it shouldn't matter the operating carrier, they should have the same ground experience. While I don't know who is "at fault" here, I would blame LH more than UA for excluding UA when it is LH who may be "forcing" its passengers onto UA operated flights and then denying them access to the FCL's. The same argument can be said of earning HON miles on UA transatlantic flights.