I have heard and I wish him well. Going through cancer treatment isn't easy for anyone - and being a king doesn't make it less unpleasant and or less debilitating.
It's not old news. He thanked everyone when he had his recent operation but this is his first public statement since being diagnosed with cancer. This is the BBC from an hour ago.
I think it's more about anti sycophancy wrt royalty. A small paragraph mid newspaper (or news broadcast) would be more appropriate than kicking real news off of every front page to headline a "thank you" from Charles.