No one has any right to know the specifics of anyone else’s medical diagnosis or treatments.
Sadly, royals aside, It’s the life of a disabled person every day. There is an expectation that visibly disabled people have to tell others their life story.
People may joke “what’s happened to you then” when you are a wheelchair user and they demand to know what’s wrong with you. The information makes no difference to you, you use it for a pity party or to make your life feel better (there’s someone worse off than you).
It happens regularly to my family member who is a wheelchair user. On holiday once, a woman shouted across the restaurant “what’s wrong with him” - none of your bloody business mate.
It’s right they haven’t shared the type of cancer. It’s none of our business, just because they are public figures we don’t have an automatic right to know. We have a right to understand if they are unwell or working / not working, but the specifics, nope.