When I started reloading in the latter part of the 60's it was mostly for rifles. You would pick a load from a manual, then acquire the bullet, primer, powder and case used and assemble the round. Even the loads for my 25-06 AI were listed in the Ackley manual.
After nearly 40 years of not, I started again a couple of years ago, handguns only.
Just about the only bullets I have used are Precision Delta jacketed, and Missouri Bullet Co. lead, with a few Berry's and Ranier's. None have any loading data so I have done a lot of searching.
I came to the same conclusion as the OP and 125JHP--the amount of the bullet in the case should be the controlling factor.
On another forum someone maintains a database or 45 ACP bullets where people have measured the length of the full diameter of the bullet. They measure by blackening the sides of a bullet, then using a razor blade to scrape the black off and measure resulting clean spot.