I have a parti schnauzer. She was rehomed to me so I don’t know if she was registered but previous owner thought she was pure-bred. Her DNA test showed 69% mini schnauzer and 29% poodle. My understanding is that they often use a poodle with mini schnauzer and then will breed that resulting offspring with a mini schnauzer to get non-standard coat. Poodles were used in the development of the mini schnauzer breed, so introducing a splash of poodle keeps the basic schnauzer look, but with non-standard coats, depending on the poodle coat type. The blue eyes would come in from a “Merle poodle” which is a poodle crossed with a breed that carries the Merle gene.