rt3070 is a fairly new chipset, even if its not new it will take time for specific things such as rfmon to work.
I am not very familiar with the interface naming, but I believe when serialmonkey made their own versions (either hacked or from scratch) they (serialmonkey) may have separated the differences between usb and pci devices. Even at that usb and pci chipsets had different model numbers altogether.
The driver you are using most likely came from ralink's website, meaning its only capable of making a connection and that's about it (hence the sta in the driver name for station mode, I suspect).
I personally do not use airmon-ng that much as I personally see iwconfig can do just the same trick without having to make assumptions such as these when its incorrectly displayed. In many other cases airmon-ng is a handy tool I must admit if you aren't familiar with linux and/or networking in general.
rt2560/rt2500 are the drivers for ralink devices which do not have 802.11n capability, unlike yours. So I would not worry about airmon-ng incorrectly displayed and assumed the chipset/chipset range is detected much different than the driver/chipset of your device.
iwconfig calls the info from the driver, airmon-ng I believe has a set database of specifically matching ralink named chipsets and naming as it sees. In this case its probably because rt3070 isn't on the list (which is rt2870 as many posts from google show, but possibly rt3070 is usb version and rt2870 is pci/pci-e version) it will display the last one on the list/database. Meaning that airmon-ng or aircrack-ng suite hasn't been updated to take on 802.11n devices in the manner of which this specific area has shown.
bt4 pre final does not as yet support rt3070 for I presume modes other than station. This pretty much goes right across the linux distribution because ralink only releases station drivers. Your best bet is to wait for more hacks to appear and see if the work, whether it be upgrading kernel and/or using compat-wireless, etc.
Do keep in mind that rt2870/rt3070 was released much later than bt4 pre-final's release date hence the limited support.