I had a different exp regarding this . I am in Atlanta and my friend got a email similar to the one above from german embassy in SF. So I applied for transit Visa in Atlanta German Embassy and they declained it saying you do not need transit visa in case you have AP. I went there personally and showed them the letter my friend got from SF german embassy and they still insisted no Transit visa is required and in their words " Lufthansa Airlines knows about AP rules and they do not ask for transit Visa'. I asked for a letter from embassy sayiing I donot need a Visa and they charged me $25 before giving me a letter(Transit Visa only costs $18

). Never had any problem during travel any where no one even asked me for the letter. Looks like it depends on the airport where you are flying from (My thinking is bigger airports like Atlanta know about the AP and smaller Airports like denver are asking for transit visa)