Phillippines did a legal preemptive strike. Basically, it wants the court to rule everything China holding around Spratley illegal. China is not going to sit there and wait for the rulings. I think taking the case to the court directly prompt China's current action. Once the ruling comes there will no more good faith negotiations in the future. They will always under the cloud.
Basically, Philippines cut off China any wiggle room and backs it to the corner.
I really like your anaysis, it explains a lot .... but I think China also want to complete this reclamation (including buildings and facilities) as soon as possible before new US president elected in the end of 2016. I thing Chinese planners have assumed that new president would be from Republic and tougher on China and would increase defence spending significantly. So China have roughly 20 months to complete all.
Interesting to read that Philippine vice president (Jejomar Binay) openly said would cooperate with China