Hope to answer your question.
vstdev.richackard.com/doc/vstinterfaces/vst3Automation.html says:
No automated parameter must influence another automated parameter
The prime example for this is the automation of preset changes. A preset change can lead to the change of all ‘normal’ parameters. So if automation data already has been recorded for these parameters and the preset change is recorded as well: who wins? This question can not be answered and the problem can only be resolved by avoiding it. This is why automation of preset changes is not allowed by default.
Note The example in the VST SDK does set the automation flag, but also in my VST the program parameter is not recorded, not by any DAW.