Clavia has now tried to clarify all this.
String Resonance?
With the release of the Nord Electro 3 HP and the new Nord Spring Catalog 2011 we'd like to clarify what we mean with the term 'String Resonance':
Generation 1
String Resonance samples when using the Sustain pedal on Medium or Large Acoustic Pianos.
Compatible with: Nord Electro 3, Nord Electro 3 HP, Nord Stage Classic.
Generation 2
String Resonance samples when using the Sustain pedal on Medium, Large or XL Acoustic Pianos.
Sympathetic Resonance between keys held down simultaneously, regardless of the sustain pedal.
Dynamic Crescendo
Compatible with: Nord Piano, Nord Stage 2 and Nord Stage EX (OS v5.12+).
It was taken from this link on Clavia's website:
http://www.nordkeyboards.com/main.asp?tm=Libraries
Hope it helps. (Ask if you still don't understand)
Best regards.
Cbas