I looked into this and you are correct. But it appears that Mann was still less than 100% honest about receiving the Nobel Peace Prize.The IPCC was awarded the prize, and what they did was acknowledge the work of specific scientists who contributed to this achievement, including Michael Mann.
I don't know how Mann told people about this acknowledgement, but it hardly rises to the level of a career destroying scandal.
Mann is a highly regarded scientist in the field of climate science and has won many prizes and accolades for his work.
In science, fraud constitutes faking results, and Mann has never done that.