Why do many Western scholars use the name Hmong-Mien instead of Miao-Yao?

Many Western scholars prefer the term Hmong-Mien over Miao-Yao to avoid conflating linguistic classification with ethnic and political categories.1

The designation "Miao-Yao" is of Chinese origin and is tied to the concept of "nationality," which incorporates factors such as culture, politics, and self-identification rather than strictly linguistic criteria. For instance, in China, the "Yao" nationality includes speakers of Mienic languages, but it also encompasses speakers of Bunu (a Hmongic language) and Lakkia (a Tai-Kadai language). Conversely, some speakers of the Mienic language Mun are officially classified as part of the "Miao" nationality.1

Because these ethnic labels do not align consistently with the actual linguistic groupings, Western scholars adopted "Hmong-Mien" to provide a more accurate and distinct terminology for the language family itself, thereby preventing confusion between ethnic identity and linguistic affiliation.1