Fifth freedom rights are far from unheard of in China. The Chinese government has given them out for development of air hubs in smaller cities, particularly for cargo.
http://www.chinaaviationdaily.com/news/4/4800.html
It wouldn't surprise me if China were willing to give DL a limited set of fifth freedom rights -- say, rights to serve SIN and BKK -- as an incentive for DL to move its Asia hub to PVG and funnel more intl-intl traffic through there.