Adding Ground Wire to Existing NEMA 10-30 socket
The cord lengths described in those documents involve the cord between the wall and the charger.  Looking at the item on the Web, it appears its cord is quite short, and certainly compliant. 

The 25' cord you speak of is between the charger and the car, and that's a non-factor. NEC doesn't regulate that cord nearly as much, because it protected by the charger.  NEC never intended for you to need to park the car so its port is within 6' of the charger. That would make every public charging station illegal and impossible, for Pete's sake! 



Retrofitting a ground wire is pretty straightforward. You can run it as a separate bare wire to any of


back to the panel the circuit is powered from 
any junction box for any  other circuit that is grounded and comes out of that panel... however, the ground wire must be large enough, you need a 10 AWG ground, so a 12 AWG ground won't do. 
any junction box fed by non-flexible metal conduit back to that panel
the Grounding Electrode System, i.e. The system of grounding wires that connect the service panel to the ground rod