OK, you say the DTCC is completely concerned about the certs that are in the system. Previously you have said that the DTCC doesn't care about which certs are valid or not, that such a determination was the responsibility of the T/A.
If the DTCC is, as you say, nothing more than a book ledger system and, also as you say, the T/A is the only entity responsible for the validity of the certs in the system; why would the DTCC be completely concerned about the certs that are in the system? According to your messages, that concern is completely outside of their realm of responsibility.