Me, personally think that Ginebra wants to have Greg on their roster only to be traded for Cstand. The Gin Kings have aleady proven that they can win a championship even without Greg Slaughter on their line-up and no one can argue that. Though i think that Tim Cone wants to have Greg back but the final decision is up to the management, c/o Alfrancis Chua and we all know that sometimes this guy makes a harsh decision.
Is the rumor about that is true? That Slaughter to CStand has never been proved to be true. But same with you, I'm also with the impression of that why Greg decided to finish his contract.
But come to think of it, if Greg will sign a new contract then he can take look at the new details including the part wherein he can't be traded. Since that will be a fresh contract, there would be a new and fresh term (player protection) instead of his old contract that he will just re-sign.