its a specific type of language, not all language are the same , the nature of that specificity is the main point of the the claim made in this article
all languages are embedded in some domain, therefore having a domain does not make a language "a specific type of language"
Many languages are in fact designed and publicized as general-purpose programming languages.
People have settled on the term DSL to identify those languages whose domains are highly constrained as compared to more general purpose or broad domain languages. This usage exists whether or not you think the term itself is stupid.
I know what they meant to do, but they've drawn a line where no line exists and the result is confusion.