The Grandiflora Class was created to accommodate Rosa x 'Queen Elizabeth', as it was a hybrid that combined the flower size of the Hybrid Tea with the larger flowers clusters of the Floribunda. Rosa x 'Queen Elizabeth' was named and introduced to honor Elizabeth II who had been crowned only a year earlier. I suspect that part of the reason for creating a new class of roses was to add additional marketing hype to this introduction. The flowers are medium pink and moderately fragrant.
I agree, the rose marketed as All Dressed Up™ (Rosa x 'WEKgrasucejuc') is an intriguing Grandiflora that can appear quite variable in different photos. It was bred by Christian Bedard, and introduced in 2018 by Weeks Roses.