entering Shanghai on MU ticket, leaving 48 hrs later on separate UA ticket

I am American and flying on China Eastern from Hong Kong to Shanghai, staying 2 nights and then leaving on a totally separate booking and United Airlines ticket to San Francisco. The SFO Chinese Consulate web site says in order to obtain the 72 hr transit permit the onward ticket ( leaving Shanghai) must be an "interline ticket" meaning the MU( flying HKG/SHA on China Eastern/MU) and UA flights would be on the same reservation/ticket. I think this "interline ticket" info is incorrect. I have 2 different confirmed reservations and 2 tickets. Is that okay to get the 72 hour transit visa? Some people arrive by boat and leave by air and they obviously don't have an interline ticket.