Not his fault, he probably reads the BMW literature. They quote the dry weight of the GSA somewhere around 490 lbs (guess he's rounding down). For BMW dry weight means no fluids of any kind, and no battery. Add those insignificant components and the weight goes to around 575 lbs. Considering they hold almost 9 gallons of gas, that's probably not too far off.
Had a GS before the R3T. Probably the single most competent bike I've ever owned.