Because there are people out there who want to start with clean worksheets to work with and populate them with their specifications.I'm not sure why they would send you an incomplete reamer print form. That's a red flag.
I'd avoid PTG, maybe they've changed but from my personal experience and all the horror stories you hear it's surprising they are still in business.
JGS or Manson should be able to help you out with a reamer if this fails.
FWIW this is what a reamer print should look like
My go-to gunsmith has a pretty good relationship with PT&G (and other reamer makers) without any issues. My chamber reamer for my .338 Thor was built by Manson (before he retired), but my sizing reamer was by PT&G.
For my .338 Thor (NMI), I asked Manson for their .338 NM. I crossed out the measurements I wanted to improve. I submitted it to them, and they returned a reamer printout with all my changes.