It is unfortunately a mixed message they are trying to present.
(Perhaps a tad analogous to the "Tesla is not a Lotus" situation)
GM wants people to think of the Volt as an EV, not a Hybrid.
If they advertise the full range (including running down the fuel tank) then they admit it is a hybrid.
If they advertise the EV only range (40 miles) to suggest you could just plug in frequently to avoid ever using the gas motor, then it ends up sounding like a very pathetic EV.
Their marketing department probably needs to get more creative, or else this is just the makings of another FUD machine, EV1 type experience. (We built something but don't really want to sell it).