"The fuel tank capacity is 9 liters / 2.38 gallons with a 2 liter / .5 gallon fuel reserve." -pg. 41, W20 Engine Technical Training, ST1403a, 2/12/2014 ed.
Assuming USG, the way I read that, 2.38 gallons is the total volume of the tank and 2.38-0.5 = 1.88 (1.9) gallons available. I do not believe coding allows running the tank dry, so the maximum additional usable capacity is simply not 2.4. People might be overfilling to stuff 2.4 in, but the vapor canister error is in their future if done on a regular basis.
As suggested, perhaps the LCI simply has a larger tank, but this discrepancy has existed since before the LCI was introduced, so I think a lot of people just aren't paying attention to the amount going in, or they are overriding automatic pump shutoff.
2.1g +/- a tenth or so is all I have ever gotten mine to take without overriding the pump shutoff, so coding really only added 0.2g of usable capacity, and that clearly jives with the tech specs.
