Counterbored tube. fig.9 P.16 here
http://www.atsb.gov.au/media/2888854...y%20report.pdf
Drawing error perhaps ?
Misinterpretation of geometrc tolerancing requirement, at design, manf. dwg. and/or inspection?
The misaligned counter bore is so obviously visible by eye that one could imagine inspection querying drawing intent - and if no one really understood and 'didn't like to ask' - Curtains !!
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