I disagree. If the Captain, me or even one of the RFOs feels we need an extra hour of gas and has a valid reason, there's not a dispatcher in the world that's going to get that jet to move without the extra uplift. There's been times that dispatch ACARSed asking for a reason for the extra gas and the Captain's reply is simply "because I want it". It's only different in the 121 world if you let it be different.