Additionally /dʒ/ is a single distinct sound. There is no /d/ sound in /dʒ/. It's an unfortunate issue that IPA notation might make it appear as though /dʒ/ is the concatenation (borrowing a programming term) of /d/ and /ʒ/ when it is most certainly not. The author's assertion might make sense if affricates such as dʒ represented multiple sounds, but I am not aware of any linguists that subscribe to such an idea.
So when we say "the D is silent" in the word Django to other English speakers, we are implying that there is no /d/ sound at the start of the word, and that would be correct. The author's argument does not make any sense here.