Yep- about the only correlation between the Chevrolet car and the Chevrolet brothers was the name. If I recall, Durant died penniless managing a bowling alley, while Henry Ford was in control of his company almost until the end, even though he was, by most accounts, totally senile. And the Chevrolet brothers resorted to making speed parts for Fords. Chalk one up for Fo Mo Co!
As to the question at hand, technically speaking, no, it's no longer a flathead, but since it began life as a flathead, it will always be a flathead. In every magazine article you read, such a setup is ALWAYS described as an ARDUN flathead.