This is normal with WrpEdit.
When you run WrpEdit and use File....New, you get 2 textures by default:
data\more_anim.01.pac and
Eden\ps.paa
It has never been any different with WrpEdit and Installing Resistance or not makes no difference to WrpEdit, it doesn't actually see the Res folder anyway.
On the other hand when you load an island that you have added textures to, the extra textures will also be in the texture list.
If this is not the case, then, are you sure you saved it after adding them?
Planck