It’s the contrast between this and the assertion in your post ‘most people agree....eternal’. If you accept that God is eternal then concepts involving any relation to time like ‘before’ or ‘after’ etc don’t apply. There is no before or after in eternity, there just is, and God ‘is’ in eternity, i.e his existence and nature are complete and absolute, not subject to the possibility of change or having been different at some point. He expresses different aspects of his nature in different ways, but these expressions are not differences in his nature, just different expressions of it. For your question to be applicable, God would need to be bound to time, to have had a beginning in time, and that is not the God of the bible.