The idea that they mean it, and that it's for publicity, are of course not mutually exclusive. For me the weirder thing is how many people who usually believe in Death of the Author are suddenly taking a director's interpretation of their work as canonical. As is so often the case, ideological coherence takes a backseat to the needs of the political or cultural moment.
Anyway, the tougher question is how conscious either of them were of this at the time. It's easy to imagine this was all deliberate, but it's also easy to imagine that it was subconscious, or that it wasn't in their minds at the time but the film's themes are sufficiently broad enough to reinterpret in light of new facts (if they told us in 15 years it was really about slavery the whole time there'd be tons to support that, too). Also fits that making a film like this gets you interested in the philosophy of identity, which prompts questions, which...et cetera.
Anyway, the tougher question is how conscious either of them were of this at the time. It's easy to imagine this was all deliberate, but it's also easy to imagine that it was subconscious, or that it wasn't in their minds at the time but the film's themes are sufficiently broad enough to reinterpret in light of new facts (if they told us in 15 years it was really about slavery the whole time there'd be tons to support that, too). Also fits that making a film like this gets you interested in the philosophy of identity, which prompts questions, which...et cetera.