It's also important to bear in mind that the situation in 1220 may not be the same as it was in the past.
So, some Greek 'gods' may have been supernatural creatures that people came into contact with and that people thought were gods. Which will lead to stories being told about these 'gods'. Eventually faeries will pick up on this and take on the role of the Greek gods. However, the original creatures that prompted the first stories (and may now be long dead, or lost in their realm) might have been magical, or infernal, or divine, (or indeed merely other faeries).
On the contrary, Apollon is explicitly stated as faerie in The Sundered Eagle. I don't believe his realm is discussed in Ancient Magic, but just because he has a group of Magic-aligned followers, this doesn't imply he is magic in nature. The status of Hermes is under doubt, as mentioned in Chapter 11 of TSE; a plurality of Hermes is the most likely answer because there was a faerie being worshipped as Hermes/.
In Hedge Magic, Gruagach is stated to be a faerie god worshipped by Gifted magicians who now realise that their powers do not descend from their god. This is no different from Christian magi - just because they worship God, this does not mean that their powers are Divine in origin.
If you want consistency, the best thing you can do is to get rid of the magic/faerie difference. make all of them Legendary realm and it will work better. The Merinitas are the ones imposing a false division in here, since they centre their own activity in a fairly small part of the Legendary realm and think they are distinct. They are not, but that is their delusion. I see the magic/faerie divide as an artificial one imposed by hermetic scholars, not a real one. Incidentally the divine/infernal one might be artificial as well, since hermetic magic cannot detect the difference. And in any case a triad of realms is much more mythic than a quartet.
One certainly might wonder why a faerie Apollo is the source of an extensive explicitly magical tradition, based on hymns to the god, and is the sacred ruler of an enormous magical regio beyond the North Wind. Likewise, the Grugach story divorces the Grugach magic from its original (and, imo, much more interesting) origin story as remnants of old sacred traditions.
I tend to look at the different realms simply in terms of their measurable effects. This aura does such and such, this one does the other such and such. I personally don't find the larger system convincing in a metaphysical sense so I don't find it productive to go there in too much detail.