I can't really see what, if anything, is all that heretical in these theologians' definition of the Trinity. I just don't understand why they think they need to rewrite tradition. Haven't we had a functional dogma of the Trinity since A.D. 325?
The Nicene Creed says nothing one way or the other about subordination; the closest thing the west has to a definition against it is found in the Athanasian Creed, in which say in one place: "And in this Trinity none is before, or after another; none is greater, or less than another. But the whole three Persons are coeternal, and coequal.
" but then says further along that Jesus is "equal to the Father, as touching his Godhead; and inferior to the Father as touching his Manhood.
" I gather that some Catholic writers want to cast the Eastern churches as subordinating the other Persons to the Father.
I looked at some of Giles's book, and it appears to be the sort of thing where you need to read quite a bit of to get where he is going. Giles is a conservative Anglican, so I would guess he takes the western approach above.
There is a tendency towards restorationism in evangelical thought, so they tend to fail to pay attention to the history of these arguments.