I own a RB-532 running MTv2.9.13 equipped with a CM9 similar mini-pci wlan card with the AR5213 chipset. Wierdly enough, at the “band” pull down menu the option 2.4GHz-G-Turbo is not availablle.
The same type of card is also installed on a PC with MT v2.9.6 and works perfectly with that band option.
but this is not the fix, it is only the workaround as the wireless-legacy uses older wireless driver which doesn’t check the eeprom for supported bands.