I think that this is correct:
Let’s say that I have a string (at rest) and I tap it just before the 19th fret with my finger. This will result in two vibrations, where one is from the nut to the 18th fret, andone is from the 19th fret to the bridge. The vibration between the 19th fret and the bridge is heard via the neck OR bridge pickups.
Now, let’s say that I have my (arbitrarally) chosen pick, the Dunlop Flow 2.0mm [in Ultem], and I hit an empty string but keep the pick on the string (in other words, impact with no release). I think that I will have triggered two vibrations, one between the nut and the pick, and one between the pick and the bridge. I think that the pick is behaving like a fret in this case, and if one has the bridge pickup turned on, and picks in a standard location, the “chirp” will be obvious.
I’m not saying that I can play slide guitar with one of these picks, but that would not be a big exaggeration.
So it seems to me that the “chirp” is an impact property, and has nothing to do with the release.