That is more of our expectation rather than an onus on the part of the destroyer. Judging from its armament and propulsion, it was not there to deal with the PCG ship. However, since it is sent, there must be constraints on where it could go. In SCS there are often foreign naval vessels "exercising FON" so the destroyer can't just leave. The argument that the destroyer is at fault for not leaving just doesn't work no matter how you many times you repeat it.
The issue isn't whether something could happen but how likely it is to happen. Given PLAN's institutional track record, standard competency of personnel and reasonable rules of engagement should be the base assumptions. Baseless speculation on deviations are as waste of time as worrying about being striked by lightning.
What more likely happened is that the Filippnos are already accustomed to Chinese rules of engagement to stay one step ahead.
I think we will have to agree to disagree here.
I do agree that in general PLAN competency as a baseline is to be expected, but everyone makes mistakes, whether it is at the planning level or the real time command/tactical level.
The PLAN went into this with the correlation of forces on their side -- it should be reasonable to expect they knew how to use it and how to mitigate the usual PCG tactics.