Sorry for unclarity--that's not my query/assertion. Assertion: looks like a commercial adapter. Query: why use the commercial adapter if you are already milling

Sorry for unclarity--that's not my query/assertion. Assertion: looks like a commercial adapter. Query: why use the commercial adapter if you are already milling a custom bit? There are probably some practical answers to this if I gave it enough thought. Like, the CAD file to mill a hex bit was already available to NASA; or, it kept the overall length the same so the clamp could be developed in parallel.