Run the following bit of code using hoch.github.io/canopy:

/ @channels 2
// @duration 1
// @sampleRate 25600

// Don't remix to stereo, so we can see all the channels.
context.destination.channelInterpretation = 'discrete';

let s1 = new OscillatorNode(context, {frequency: 440});
let s2 = new OscillatorNode(context, {frequency: 880});

let upmix = new GainNode(context, {channelCount: 2, channelCountMode: 'explicit'});

s1.connect(upmix);

let f = new BiquadFilterNode(context, {frequency: 1000});

s2.connect(f);

f.connect(context.destination);

s1.start();
s2.start();

if (0) {
    upmix.connect(f);
} else {
    context.suspend(1024 / context.sampleRate)
        .then(() => upmix.connect(f))
        .then(() => context.resume());
}

let stopTime = 0.25;
if (1) {
    s1.stop(stopTime);
} else {
    context.suspend(stopTime)
        .then(() => s1.disconnect())
        .then(() => context.resume());
}
 
Examine the graph at some time after 0.25 sec.  There is a strange glitch here the second channel becomes silent.

But the code never does anything at this time.  s1 is stopped at time 0.25 and that's the last time there any change in the graph.

It's as if s1 is disconnected at this time, disconnecting the gain node which disconnects from the filter.  But this is an offline context, so I was expecting the disconnects to all happen very close to 0.25 sec.