Scythian is a catch-all term meaning 'barbarian from the east,' and it shows up in Greek and Roman texts talking about all sorts of different people-groups (even the Goths get called Scythians by many Roman authors, despite having nothing to do with the eastern steppes). As a result, the real answer to the question depends on which text we're talking about. Herodotus talks about Scythians who may have had something in common with steppe nomads, but each ancient author uses the term differently.

It's only recently that historians have come to realize that references to 'scythians' in historical sources don't refer to a single people group. In the late 19th and early 20th century, when anthropologists and scientists were arguing that racial differences were objective and measurable (and not arbitrary social constructs), historians assumed that the scythians were a single, unchanging people group with objective racial and cultural traits (hence, the quote you gave). The fact that ancient authors always talked about scythians with rote stereotypes lined up with how contemporary scholars of race used stereotypes to describe living peoples in the late 19th century. It was only after we began to reconsider the way in which we talk about race in the late 20th century that scholars realized the ancient sources were slapping a stereotyped label of 'scythian' on any barbarian group that came out of the east. Since this realization, historians have started to be much more careful about this term (and other names for barbarian people groups), taking care to assess whether the author is talking about a real socio-cultural group, or just using 'scythian' to lump together random outsiders they've never talked to the same way your racist great-aunt might talk about 'the Mexicans.'