Yeah, I recall that several of those releases were issued long after you guys had confirmed the deals by other means. Lessee ... you had both McIntyre and Chambers in a story on the 26th, but the archives over at bb.com show Mar. 3 for the McIntyre release, and Mar. 4 for Chambers.
(Strangely, though, they got the one for Owens out within an hour and a half of his press conference ... )
For the others, I'm guessing they wait until the signed contract has been approved by the league office to make the official announcement?