To be fair, even William made statements about the press hounding Kate and comparisons with his mother , but to my recollection I do not think he ever used a major tour like this as his platform. In fact I don't think I've seen something like this tour used as a platform for this kind of thing before.
As said, I thought Africa and the message they were giving there was critical to them, so it makes no sense they would chose to over shadow it and use it as leverage in this way.
It is not dissimilar to the private jets they were taking then launching a travel company to support the environment.
It does make you wonder how genuine they are being about their causes.