It is possible DF-31A is in fact 11000km range? But I believe that will come in the expend of sacrificing payload. Probably DF-31 is only one single warhead.
The new DF-41 will have longer range(12000km-15000km) and much greater payload which resulted in MIRV.
The PLAN just started the SSBN strategic patrol. Given the highly congested shallow SCS and North Sea. I doubt one of the criteria of Type094 SSBN require to venture into Western Pacific Ocean to fire within US mainland continent.