I don't think we should read too much into the LE statement. It feels to me more of a "leave us alone, we're working" statement, rather than anything else. This is a high-profile case, and the media, as well as the public, have been clamoring for information. LE likely needs some space without having to deal with public anticipation.
DN may not have answered any questions (as is his right), whether or not he has an attorney. Ballistics examination and DNA comparison can take weeks to complete. Yes, it is possible to get these things done quickly, but that doesn't mean that they can get them done quickly. We don't know what the load at the forensics lab may be. These investigations can take time. To me, the statement says that DN is still a person of interest, but they have not gathered all of the data at this time.