It seems like calling for people who are connecting on specific flight numbers puts a little reality into the situation... like maybe those flights are being held a bit for the folks connecting, or at least someone has done some research to determine they can still make the connection if they hurry (which may or may not actually be the case).
Just the blanket 'we are late as usual so please let people who have connections leave first' has gotten about as predictable as a credit card pitch, so I don't think people pay much attention.