The Alans most certainly weren't especially Byzantine in culture- though the Armenians and Georgians are much more easily explained being together (when I said earlier I had meant that Georgians and Armenians shouldn't share a group with each other, not in relation to Byzantium). They certainly had quite a fair bit of interaction with the Byzantines, including a marriage to a woman who was half-Alan, and though they did indeed (partially) Christianize the Alans, I'd not call their own culture too close to that of the Byzantines, nor to their general allegiance at any rate particularly stronger than others.
In fact, as if to show such a divided history, the Alans are in the Byzantine culture group, use Russian graphics, and follow Tengri. I'd say that their largest motivation for being in the Byzantine group is their Orthodox status at later start dates and their position near to the Caucasus while not being Turkic themselves. Their connection to the Byzantosphere is much weaker than that of the Georgians and Armenians, though not as weak as that of the Assyrians. I'd say the Assyrians are easily the most distant for a plethora of reasons.
There is one thing I shall eagerly agree on, though- The Byzantosphere certainly was great.
EDIT: As a side note, I don't have a problem with the Alans being in the Byzantine culture group. I can't really imagine where else to put them, except maybe Iranian, though I think their connection to the medieval Persian world is not strong enough to warrant that and it'd mostly be for graphics.
An argument could be made to give them there own pagan faith, as they sure as hell weren't tengri worshippers...