That mutual defense treaty with the USA Marcos has in his back pocket seems like it's on the verge of being thrown on the table what with Marcos stating if one of his people are killed by the Chinese he'd declare it an act of war.
Can't say how this treaty is affecting China's temperament in the contested zones but I'm sure Xi wouldn't want the US Navy escorting Filipino naval assets that's enforcing their legitimate economic zone in the area that China is, historically speaking, staking claims as the new kid on the block when the Chinese illegally created the 9 dash line in the early 50's. The International Court decided it was invalid and also decided in the Philippine's favor circa 2013 that the Chinese ships harassing and blocking the Filipino ships operating in the area was illegal and the Chinese have simply ignored it.
That China sees itself as being illegally contained by its rivals in the Pacific, makes for some real potential for armed conflicts to occur sooner than later.