I agree with your perspective as well. The bushing/shoulder is a small nuance that is hard to get everyone to agree on.
The machinist/perfectionist perspective is that using a thread to locate a hole is not the right way of doing things
My perspective is that with a tight clearance hole, using the thread to locate the is probably one of the smallest sources of error in the entire stack. This topic on framebuilding tolerances puts this discussion into perspective
In this case, I think the bushing press-fit design can satisfy different people’s expectations of accuracy while adding minimal cost.
From my perspective, the goal of the open fixture is to create the hardware to allow people to remix or modify. If someone wants higher tolerances, they can modify the CAD to use a more precise locating method. The initial design release will probably be the M8 thread, just to keep the cost down and BOM low.
That is a good suggestion. I think once the hardware is tested and adopted, adding variations is possible. But for now, it might be trying to do too much at once.