This type of has been explained in previous questions. In short, it expresses the speaker's surprise or disagreement.
* ~ why is there a here?
* Is grammatical?
* i-adjective followed by
This type of / comes right after a predicate in . You cannot put when is used as a subject (e.g., ) or an object (e.g., ). When is used as a predicate, and are interchangeable because already has a nuance similar to , but I feel the sentence sounds more emphatic with .
**EDIT** : is a na-adjective, and thus can take without the nuance mentioned above (e.g. ?). Still, the combination of typically has a surprised nuance regardless of the word class of the preceding predicate.