We see a lot of dogs who were suspected to be terrier mixes, but aren’t. Though some terrier breeds have a wirey, “scruffy” coat, dogs with no terrier ancestry can also have this trait. A gene called RSPO2 confers this wire-haired coat (often referred to as “furnishings”), and a dog only needs to inherit one copy of this variant in order to have this type of coat.
What many people don’t realize is that a lot of low-shedding breeds such as Poodles, Shih Tzus, and Bichon Frises have this same genetic variant. In those breeds, that trait often interacts with other coat characteristics such as length and curl. But when breeds mix together, some dogs, like yours, may inherit the furnishings but not the curly or long coat. This can make a dog look a lot like a terrier, especially if they have pointy ears from Chihuahua or other breeds.