"All Gods are one God, All Goddesses are One Goddess"
I attribute this to the inability of western people to relinquish the monotheistic belief systems they were exposed to as children. Invariably I meet people in the pagan communities who were raised as christian. The result is they cannot grasp that each culture has a pantheon of distinct gods and goddesses. Each has their own personalities and attributes.
The concept they ascribe to goes even further with the union of the One God with the One Goddess to becoming the Universal One.
I try to explain to them. Nope. Sorry. Not how it works.
For instance, BrĂg is not Estanatlehi nor Auset nor Kali nor Astarte nor Diana nor Hekate nor Aphrodite nor Ameratsu, etc.
Unfortunately quite a few cannot grasp the reality of the spirituality and religious systems of other cultures through the millenia.
In order to feel comfortable with their having left the structured monotheistic christian religion they are creating their own monotheistic one by using such a phrase in describing their new beliefs.