Two points:
1) VSL is different from most other libraries in that it is sampled without room ambience, so that you can customize it to your own needs. Most other libraries have room ambience (reverb) as part of the sample, so you're stuck with what they give you. You could always add more, but you can't subtract. Additionally, since VSL is a very large library, the samples that you get in the Jam Pack are just a small subset of what VSL's full package provides. So if the articulations in the Jam Pack don't sound realistic to you, perhaps you are in need of articulations that aren't provided in the small subset that Apple gives, and you may also need to customize the effects to taste.
2) No one has told the original poster how to access these Jam Packs in L8.