Intra-china awards increased to 17.5K miles. What you are seeing are instances of broken fare awards which DL has been pricing out for a couple years now. You can see the fare construction by bringing it up on the website and clicking on the fare rules. You will see the 35K awards are a combination of two separate 17.5K awards due to the connection (fare code YSM175). You can find 17.5K awards on this route on the CZ non-stop flight. There is nothing inherently "incorrect" with broken fare award pricing. They are presented in cases either where there is no inventory available on a through routing (due to married-segment logic) and the broken fare is either the only option, or it is a cheaper option than whatever award bucket is available on the married-segment through routing.
However as per RM (multiple awards in last few months had to deal with them) these should price as one award. One of the most common to incorrectly cause a break was a flight to/from SHA instead of PVG. Per RM these should be 1 award, but not everything is marrying correctly. Theyve overrode for me, but it is a hassle to even get to them. Reservations just insist on telling you that its the new price. Usually I had to get them to see it was breaking into 2 awards to contact RM.