As a matter of fact it was very deliberate, and there's two main reasons why; first, announcing yourself as the Miller makes you a target for the mafia, and second, I would be taking a big risk that people would believe Raven instead of me.
With so many mafia around, it was safer to remain unknown and play along until I could call him out at a safer time, which is now. The two most likely outcomes of me counter-claiming Miller now are: 1) Raven dies, 2) I die.
Had I counter claimed immediately, I would have risked death, and then if I had survived I would have risked being killed that night. After all, the mafia would know that I'm not mafia, so they would know that I'm town rather than an independent, and I'd be a nice easy target whenever it was convenient for them to kill me. On that note, do please notice how Raven has survived since his claim, despite being the only person who the mafia could be certain was town (if he is telling the truth).
Now, however, I either die or we win the game. I think this was the only reasonable time for me to counter claim.