However ... if indeed you have made perfectly clear, on the phone, that you needed a horizontal seat, AND you were given the wrong information, then I think Air France owes you an explanation. More than an excuse, a real explanation (in detail).
Agreed, I think it is fair to ask for a response. OP researched his options and called for confirmation when it wasn't clear online. I miss how the responsibility of OP to get that information confirmed (the lie-flat seat) extends beyond this? The airline rep seemed well-informed on the situation and gave incorrect info - that is simply not good and goes against the airline's 'promise'.
I know this goes against the thread's consensus, and by no means do I know better than the far more experienced flyers here, but I would say that AF could at least respond to that.