But, again, as Green says, that's exactly the problem: he didn't tell Sisko beforehand for fear he'd stop him or at the very least whine and whinge to his face even more than he did anyhow. When Vreenak boarded his vessel and headed for home, Sisko himself should have approached Garak and asked about extreme fallback plans. War is war.
If Sisko disagreed with Garak that he did what Sisko would have wanted, Sisko should have continued to kick the crap out of Garak. Instead, it was a denouement. Sisko knew that he had been exposed.