I believe these issues have been highlighted to VSL a long time ago. Unfortunately, it did not get the attention it deserves. I believe that sympathetic resonance and silent keys are necessary features to create a realistic playing experience, but VSL has ignored it because users assume that the features are there (since they are basic), and only realize that they are missing after making the purchase and playing with it for a couple of days. I speak from experience.
VSL is ignoring it because it does not hit their bottom line. However, I think it will hit sales once people get to know about it. I, for one, would not have made my purchase if I knew of the missing features.
VSL is of the view that they should spend their resources sampling new pianos because it looks nice in their annual marketing drive. The way to change this is to make this lack of essential features known across all VST forums. I believe very few serious pianists will bother with VSL if they know that silent keys and sympathetic resonance are missing in synchron. Once it hits their sales numbers, VSL will be forced to put it in their development roadmap.
Let’s start a campaign to disseminate this information? I am sure we can conquer this.