Is BTW (British Traditional Wicca) the only valid form of Wicca?
Gardener may have come up with the religion, but it has changed a lot since the 50's, 60's and 70's. For example, we have better information now, and no longer believe that Wicca is an ancient religion. Gardener certainly did. And, in no way do I recall ever reading that one has to worship Deities from the British Isles to be a Wiccan (google: Why Wicca isn't Celtic).
Christian Wicca isn't about worshiping the Christian God, and a bunch of others. Most replace the Goddess and God with Yahweh, and the Sophia, or sometimes Mary.
The label "Christian Wicca" is a misnomer, as in practice it is normally neither Christian nor Wiccan.
However, I will never understand why some Wiccans get so bent out of shape about this.