What defines the fade-out time for “built-in” sus pedal mode?

In my program the Sustain box is checked so the sustain pedal chokes the currently ringing notes. But where the release time (how fast voices fade-out) is defined? By which parameter?

Are you asking how quickly the notes fade out after releasing the sustain pedal?

I think it depends on the amp envelope and the release settings of the zones.

Yes, that was my question. And if it depends on zones envelope then I can not have different release speed, say, for onRelease (release of a key) and onController (release of the pedal) actions? They both will be the same? And if I want them to be different I should override them and script each by myself using fade() command?

I would try modulation matrix. Set the midi cc64 as source and amp envelope release as destination. I just quickly tried with a simple synth zone and release set to 1 second. Negative modulation amount seems to make the release shorter after releasing the sustain pedal.