How does it help do that?
The U.S. DOT (not China) determines which US carriers get the slots allocated to the U.S.
I agree with you - China has nothing to do with whether Delta ever gets authority to fly to China. Only need to butter up the DOT decision-makers for that.
Alice used the term "landing slots," however, not "route authority" or "frequencies," the two things awarded by the DOT. So was Alice using language inartfully or are there actual landing slot issues at PVG or PEK?
My guess is that Alice was using the term "landing slots" to refer to the right to fly to China, not in the "slot restricted sense."
CO, AA, NW and UA don't seem to have experienced any difficulty getting appropriate landing slots at any of the China airports to which they fly. With so very few total frequencies between China and the USA, landing slots shouldn't be an issue (compared to NRT or LHR or JFK, where appropriately-timed slots are very crucial and sometimes impossible to obtain).