Maybe it's the semantics I object to. If you say something is therapeutic, don't you mean it makes you better? Cures you of some symptom? Maybe all these people want to know is whether writing my memoir helped me cope with my mother's illness and death. And yes, it did, but not for the reason they think.
I recently read an interview with a writer who did say that writing her memoir about her mother's death was therapeutic for her. She even went on to add that she didn't need to see a counsellor because she'd written her book. Good for her.
For me, the writing process was engrossing and technically difficult, so it helped me in the way that work is often helpful: doing it kept me engaged and transported me to the place where I am most myself. But as far as being therapeutic, that is helping me to come to terms with losing my mother to Alzheimer's, it wasn't at all. I still found the journey heart breaking and it still hurts now three months after her death. It was an awful way to go and that's all there is to it.