It also has to with China not backing anyone. I know a well connected person. He was quite reliable with predicting what Zhongnanhai will decide on some matters. He recently said me there are rumors about Marcos requesting a guarantee from Xi in case he get couped. You know, all of the PH's military high-brass is US connected. Xi declined. Marcos flipped to the US side after that refusal of course. The threat of violence trumped over money once again. Now the PLA might have a one more attack vector to deal with just because China decided to not involve itself with Filipino internal affairs. Non-interventionism at its full glory...
That would require China to physically invade the Phillippines in order to rescue and protect Marcos and his family. Besides, the PLA would be forced to have a slug-out fest with the pro-coup Filipino military in the narrow streets of Manila and the mountain ranges of Leyte.Security protection. To avoid getting "exiled" like what happened to his father when Marcos Sr. was flew to Hawaii without his awareness. The family thought they were being flown back to Marcos Sr. political power base, which is in Ilocos, Philippines but they were instead peacefully couped and stationed permanently to the island state of Hawaii.
The optics would never be good for China, especially in the eyes of other ASEAN member states who have territorial dispute with China in the South China Sea (Vietnam, Malaysia, Brunei, Indonesia). What if the PLA invading the Philippines is seen by Jakarta, Hanoi, Putrajaya and Bandar Seri Begawan as China's method of solving their maritime disputes in the South China Sea?
How do you think that these countries would respond as a follow-up? Just take a look at what Finland and Sweden did after Russia invaded Ukraine, and I think you have the answer.
Furthermore, what if the US decides to intervene and backs the pro-coup military/post-Marcos pro-coup government of the Philippines? Would this become a China-US war over the Philippines? Also, what if the US decides to distract China's attention by opening another front for China to deal with (such as over Taiwan and/or the Diaoyu Islands) when China is stuck fighting in the Philippines?
If said exchange is true, no wonder Xi flatly refused Marcos' request.
If anything, Marcos and his family members should be the ones taking a private jet and self-exile to China for political asylum in case he foresaw that a coup by the pro-US Filipino military is inevitable.