Hi! I agree that this is a very important small detail that can really add in some life to a sample set.
In making my Kawai Baby Grand library I found a couple relatively easy ways to accomplish this for kontakt, whether it be applying keytracking to the incoming MIDI signal and setting that to a sharp modmap that changes the release time of a single envelope at a certain note # threshold, or by simply making separate groups for the top notes where the damper no longer applies and having separate volume envelopes.
Depending on the method you choose and how (or if) you plan on incorporating some form of sympathetic resonance or release samples your mileage will vary on the exact interaction between those groups and the release times. For example you might not want the release sample set to make any sound / have any samples playing during the undampened releases of the upper notes.
Anyway, cheers for mentioning this, any thought to improve the upload submission quality is always welcome here