A friend found a pic of the two of them at Yale in 1940 that he says proves the point.
Your distinction, basically implying one could not be an America First member and an interventionist later, or even at the time, is very revealing. America First was against intervening against the Germans. That’s not too hard a concept. When Hitler’s true motives and purpose were revealed in full the isolationists lost influence. True it was a tough slog because Hitler Nazism Fascism had their fans. And after the war those same basic forces wrested power from the Roosevelt ‘socialists’ and never relinquished it. Dulles brothers, Bissell, the rest all on the same side. I’m not sure why you think that document proves otherwise, when all it really proves is Dulles wanting to protect his reputation at all costs, wanting plausible deniability.