When I dropped my plat charge after it was enhanced the cancellation team guy tried to sell me on the Qantas Ultimate instead. I noted in response that it was odd that a co-branded and cheaper card was now superior in points earn than the supposed premium and much more expensive plat charge. Amex probably don't like that comparison.
I think we're being fooled and thinking about this the wrong way. These giant corporates don't easily just 'miss' the small print or fine detail on these things (usually). What seems to us to be an inexplicable blunder in their marketing is surely a deliberate strategy.
As I've posted a few times already in this thread, what that strategy actually is is beyond me ... I'm just a consumer in the end and at first glance the changes to core product seem to be a portent of doom overall for the organisation. But look here, even in the quoted anecdote, an Amex sales or retention employee, presumably well trained internally as to product strategy and direction, is, presumably, happier to sell you into a co-branded card than to retain you on an Amex "Premium" product.
They have created a product that over many years has come to be aspirational and is meant to be a marker of something. You pull your Centurion or Platinum Charge and that act is meant to say something and make you feel something. Its all marketing of course, but its worked pretty well. People are not fools though, and there obviously has to be something behind the 'black card' to make it worth owning. So, how to reform the internal cost base of their corporate machine without destroying the long built up brand? Its an open question, I have no real firm idea.
I do wonder if we'll see Amex, Australia at least (as o/s Amex cards don't seem to be suffering quite the same as the local ones), will end up being a retail model, very similar to the Diners model for Australia. A brand, a retail presence, but a "big bank" back-end and machine.