Regrettably this story is totally plausible. You can just drive out onto the runway from the float plane / private plane side of the airport. I just drove over there to verify.... Although, when I chose ROUTE in the map app from my current location (my office is a few miles away) an error pops up and says "Directions not available - A route could not be determined between these locations." For the airport official to say you have to drive past several gates and warnings, that was a bit disingenuous. Yes, there are a few signs that say Airport traffic only, duhh, and there are gates at the end of each street, but the one I drove up to just opened for me before I even reached it.