Inter-system nodes aren't L-Points. Intra-system subspace drives are quite different in nature than inter-system drives. (thus the big deal in FS1 when they could be fitted for the Altair mission)
Intra-system drives require a large gravity field to work, otherwise energy requirements are going to be exponentially higher. (which is why we don't see hundreds of small jumps from Alpha Centauri to Earth working)
Inter-system jumps require a
of energy, but enough that ships can generate them. Plus they require 'special' points in space, subspace nodes.
Technically though even inta-system drives 'activate' subspace nodes, they're just not the special 'inter-system' ones.