Yes the margin on a drill is normally ground with a back taper.
Would be nice if they were not as then you could just feed them all the way through the centerless.
Instead you have to feed until the shank area just clears through, (making it straight) open up and kick back or remove the drill.
It is not a lot in most cases and the taper per inch depends on the drill diameter. Controlling this back taper is a PITA but a given if you make drills.
You can see this by accurately measuring the mounting shank which will be below the tip width.
This backtaper is to prevent the margin from rubbing or binding on holes with decent depth as the margin is simply circle ground unlike a endmill which is ground straight but has relief.
Reamers have the same problem and are also circle ground with a back taper but less taper per inch than drills.
Some manufacturers have their own in-house numbers for backtaper but most just go by the published aerospace standards.
So he is right sort of but you have to take a bunch off the tip to see real numbers as it is a straight taper per inch along the flutes that should be maintained.
Not sure what "undersized" here means, how the resharp was done but how can you blame the machinist?
Poked the hole, not big enough. Ok, process QC, something wacky.
I like both your sides of the week long argument and would maybe fuel it to better understanding of why and what is happening.
I would be remiss to say... A big
Welcome hug to posting on the forum....
Bob