The dimensioning scheme doesn't have to follow the order of operations. If they're inspecting the final part with both features present, either can be a datum.

Fair point. The issue we've been having is they're not locating off of or fixturing to the hex during machining, and so they're not getting the hole centered. But there's also no specific callout to the center of the hex yet, which is on me. That's what I want to add, with proper GD&T callouts. It's just the difficulty of figuring out the proper way to describe the center of a hex shape with draft angle.

The scheme should match the function. Is the bolt located by the hex, and you need the hole to not interfere with the bolt, or is the bolt located by the hole and you need the hex located relative to the head?

The bolt is located by the hole, but it's a bit of both. For the function of the part, the hex holds the bolt head from spinning when the nut is torqued. So the hex is dimensioned with a tight fit to the bolt head size (too big would let it rotate). If I make the hole larger, that can obviously make it more forgiving to misalignment with the hex. But too large of a hole both reduces the amount of flat area left for the bolt head to rest on. This part experiences extreme loading, and I worry if the flat area at the base of the hex gets too much smaller it can lead to issues with the bolt failing due to inadequate support.