i think its a well calculated move. as mentioned, if trump wins, relations will likely go sour. if clinton wins, expect that things will stay the same.
but now, with the sudden change, it will force the US to rethink its strategy in dealing with the Philippines. Perhaps that is the goal all along. to let the US realize that they have not helped as much as they should have (the aid we get pales in comparison to what the US gives to its other allies). with what happened, if trump wins, most likely he wont care about it so the Philippines still doesn't lose since they have a new partner in China. If clinton wins, expect the US will likely be aggressive in trying to improve relations with the Philippines (i.e. the US might probably try to match or even surpass what China offered)
Strike while the iron is hot kung baga. At this point, dealing with China now offers more leverage than dealing with them later. And at this time, China is all open arms and welcoming. That might not be the case in the future. The trip to China has brought in huge investments, huge investments that I don't recall the US offered.