That's right H4 EAD is a benefit of green card process and not just the H1b itself. However, L2 EAD is purely based on L1 and has no bearing on the GC process.
But, the whole employment visas have to be reformed as a whole. For example, tightening H1b means, companies can start using L1 or Eb1c more. These work rounds are already being taken advantage of.
H4 dependents can only work after the primaries's green card process reached certain stage which may take few years.
But with L1, spouse can start work from day 1