The names of the articles in English are not the specific and 'inspecific', but the definite and indefinite.
That is, definiteness and specificity are two different properties of noun phrases. In English, the definite article marks a noun phrase as being definite. All the time, or perhaps with very few exceptions, a definite noun phrase is also specific.
Meanwhile, the indefinite article marks a noun phrase as indefinite. However, an indefinite noun phrase can be either specific or non-specific. The usage of the indefinite noun phrase a guy like this to refer to a known or specified individual, such as oneself, is an example of an indefinite, specific noun phrase. An example of an indefinite, non-specific noun phrase is a guy from Canada in I want to marry a guy from Canada (as in 'any guy from Canada'). But the same noun phrase is indefinite, specific in I married a guy from Canada.