If a tree falls in the woods, and nobody hears it, does it make a sound?
It’s not COTS, but rather a fabricated item and therefore presumably illegal next year. But if it really is identical, nobody will be able to tell; so it’s essentially cheating in a largely inconsequential way.
If it truly is identical, seems to me that you could just list the COTS item and its original vendor in the BOM as an alternate FISRT-legal supplier. And as Tristan said, if it was identical, who would notice or care?
Personally, I disagree with the interpretation of the example of section 8.2 example 2 EricH provided. AndyMark would still be a legal supplier of the hub and not just the plans. Therefore, any team could acquire the part without the lead time needed for it to be manufactured.
I am obviously not the GDC, but I would give the self made identical part at least one passing grade on the “would another team consider this an unfair advantage?” test.
Of course, perhaps a better question would be why would you want to make your own hub when a perfectly good COTS one is available from everyone’s favorite supplier? If it is to make it ever so slightly different, the whole question is out! Especially, the identical part better weigh exactly the same or that’s just downright cheating.