Mostly the B-2S bits are the material it's built from, like aluminium and magnesium, because it's going to be painted in NMF rather than 'carbon black'.
But there will be some radar resistant paint in some areas.
As H pointed out it already has the simpler weapons fit plus it may have an AAR refuelling probe as well as the socket for the Boeing Boom.
I'm coming to agree with those who've said this is a terrible kit. When the wings are on almost NOTHING fits, there are huge gaps all over the place, not helped by the fact that the bottom halves are quite a bit smaller than the upper halves and when they're sat in the recesses designed for them, they don't touch the sides so the glue doesn't work. I've had to superglue pretty well every joint on the model, so much so that I've run out of superglue now!
It'll need a lot of PSR on the gaps and all joint areas, and I've sanded the tops of the wings already, but there's a long way to go.
Two of the problem joint areas, LOTS of PSR going to needed here.
The port wing nicely exhibits the wash-out that's characteristic of flying wing designs, but sadly the starboard side doesn't, and I had to crack some of the joints, bend it to shape, or near, and re-glue it. It's not too bad now, but could have been better.
