He was quite clear that he was specifically not "all but saying", but did intend to reveal more as soon as it could be confirmed.
Having dabbled in Intelligence, your other points are probably correct. They are probably seeking more definite evidence. They also may have confirmation from sources they wish to keep secret, and are using this data to seek other non/less-covert sources for the same evidence. For example, hypothetically, they may have evidence from spy satellites that show exactly who was driving the SAM TELAR, but they'd like to get his own Facebook posts to reveal same.