Likely answer —we're being nerds and reading too much into it.
No—
—3 lbs of thrust isn't going to be happening, speaking from experience with model planes.
—3lbs of the air inside is compressed and weighs more is even farther from possible.
Likely—
—It only has the battery, fan, whatever when it's running, and they don't count that when it's uninflated for some reason. Like how cars have dry weight, curb weight, and gvrw.
—somewhere in the spec sheets, someone made a mistake, two people worked on things and rounded differently, some other clerical/communicative error.