yeah, you're over thinking.
I presume the deck posts will be planted in the ground. This reduces sway. As opposed to setting the post ontop of the concrete footing.
simply stop the concrete a few inches below grade. No need for the concrete to protrude above grade.
All that matters is that the deck does not sway. And that the posts are at your regional frostline. Being above grade has no bearing on those aspects.
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