Airport Exteme + external hard drive?

I have a Mac mini connected VIA ethernet and a Macbook Pro connected VIA wireless to an airport extreme. When I attempt to run time machine my external hard drive connected VIA usb to the Airport Exteme doesn't come up as an optional drive, although it shows in finder. I talked to apple tech. support they walked me through some steps, didn't resolve it, and then stated it wasn't supported by apple and I would need to plug the external hard drive into the usb on the computer (which I did and it worked). So does it just not work VIA the Airport Exteme even though apple advertises it does?

Here the hard drive I'm using Newegg.com - SAMSUNG STORY Station 1TB USB 2.0 External Hard Drive HX-DU010EB - External Hard Drives

For it to be used over the wireless connection, you need to format the disk to Mac OS X Extended (Journaled). I have my 500GB WD MyBook which is FAT32, and it isn't recognized on my network, but I have my old 160GB boot drive from my Power Mac G5 (in OS X Extended Journaled) docked in a USB disk interface also on the airport extreme network, and that is letting me select it for time machine backups. You'll have to mount the drive first by opening it from your AEBS in the finder, but it should work there.

To format the disk, connect it directly to your computer via a USB port. Open Disk Utility, and select the drive from the menu of disks on the left. Click the erase tab. Now you can select the format you want [Mac OS Extended (journaled)]. Click Erase. You're good to go to eject the disk and put it back on the AEBS. Try putting it on the station and open the Time Machine preference pane and see if it shows for you then.