I think they sign Birdman for the vet minimum, and look for the best PG they can find at the vet minimum (whether it is House, Cassell, or otherwise).
Then they will save a little money for later in the season to fill another need if either Birdman, the PG to be named later, or Giddens/Walker don't work out.
I think ownership is close to maxing out on what they want to spend this year, and they want to take advantage of the league help that comes with the vet minimum.