You seem to be missing the AMPLIFIER in my VEHICLE so BOTH the TOWER and VEHICLE can SCREAM and LISTEN.
I think what they are trying to say is that devices you might use in your car only "whisper"
Yes you would have an amp in your car... but it wouldn't be able to hook up to anything else by itself.
You could have a low-power access point inside your car though, connected to the high power equip, like a wireless bridge.
That being said 6 miles is still VERY unlikely to happen, because microwave bounces like a mofo, and other cars, buildings, etc will kill it so much faster than it would say.. a 2m radio signal lower on the band.
Wifi doesn't cut though trees very well either, for this reason wifi is usually only done in point-to-point connections where both sides are up on a tower and can physically see each other.
Being on the ground is going to hurt that very much.. If you had say a 2-300ft tower to put it up on with a high gain sector antenna on an angle you might get the range you want.. but to do this 360degrees around your house you'd need 4-6 of these antennas.. Before you know it your spending serveral thousand dollars.... Your better off just paying for a 4G hotspot in this case.
Don't get me wrong, I'd love to do high-power wifi too but... its just not that useful unless its in a mess or point-to-point configuration.