I think I have 6 threadless-headset bikes in my possession, I have two topcaps and one compatible screw.
I think the point to be made it that, functionally, if a threadless headset is assembled correctly, it does not matter what is above the stem. You can have a holster for your 9mm; you could have 9 inches of uncut steerer tube with a bright pink rubber phallus top cap; many would have both.
Spacers, devices, brackets, elastics, hood ornaments - it doesn't matter what is above the stem.