No, because Letham is a good Christian thinker. However, given his arguments against the East in Holy Trinity, it’s hard to see how he avoids it. Letham writes, criticiszing Vladimir Lossky,
Lossky’s doctrine of the divine essence…actually contradicts the historic Trinitarian doctrine. The essence is above the persons, as Lossky presents it. It is superessential. Yet Lossky can also say that God is greater than his essence. Lossky wants to have his cake and eat it, too.
Letham has several problems with this. First, he’s bothered by Lossky’s (and the East’s) insistence on the essence/energies distinction. Let that slide at the moment. He says by saying God is “above being” we introduce a new category into the Trinity. This isn’t that bad an objection, really. This is the same argument he makes against Bulgakov’s Sophiology. And Lossky makes similar arguments against Bulgakov. More on that below.
But Letham should consider if we do not place God above being, then we end up identifying God with being (this was Heiddeger’s blistering critique against 20th century theology, his Nazism notwithstanding). If you identify God with “being,” the problems are numerous: an abstract God, a limited God, an idol. And with this argument Heiddeger thought he had nailed Christianity. But Heidegger had never read the wild Trinitarianism of the Eastern Fathers. He didn’t know of Dionysius’s God outside being and St John of Damascus saying that God exists outside himself.
Long before Heiddeger the Eastern Fathers had already anticipated and silenced him. Therefore (back to the discussion), Lossky is correct in positing God outside himself. Or rather, God existing above being.
But are introducing a new category into the Trinity? Maybe. This is a legitimate problem for Letham, given his commitment to absolute divine simplicity. Given ADS, then this is introducing a new category into the Trinity. But if you don’t hold to ADS, then it isn’t a problem.
If all of this is true, then is Bulgakov wrong for introducing Sophia = ousia = glory? No. Bulgakov might be wrong for identifying person and essence (Aquinas does the same thing, but never mind). Given the trickiness of God’s relation to being, I think Bulgakov’s sophiology is quite helpful.
For a thorough discussion, see Jean-Luc Marion’s God Without Being.