Is there something wrong with my network or is this an Airport bug?

Here's my set-up:

Airport Extreme N Dual-Band connected to modem, and in turn connected to a desktop PC. (I know, save it)

Also connected to said Airport Extreme is a USB Printer and nothing else.

Said Airport is configured as "802.11n only (5GHz) - 802.11 b/g", using Wide channels, low multicast, and a different SSID for the 5GHz network.

Then, I got ANOTHER Airport Extreme (5GHz N-capable, non dual-band), wirelessly connected to the first and configured as "Extend a wireless network", configured for the 5GHz n-only SSID from the other Airport.

So far, everything should be good, no?

Now, my iphone (3gs so no 802.11n) is connected just fine to the 802.11b/g network, and my bro's macbook pro is connected wirelessly to the main router.

Here's where it gets weird:

If I go into "Logs and statistics -> Wireless Clients" for each of the airport extremes:

On the main router, I can see the second router connected as 802.11n (5GHz), the iphone via 802.11b/g and my bro's macbook pro connected the same way.

On the secondary airport, I see the primary Airport's 5GHz MAC adress as connected via "Wireless", and then my macbook, for some reason, connected via "802.11a/n"

Of course, I'm not getting the full 802.11 datarates and I'm honestly at a loss as to what is happening here.

Is my setup wrong somewhere, or is this just a bug in the Airport Extreme?