Here's what I'm going by
"How to Determine your Refractometer’s Wort Correction Factor
When taking a refractometer measurement of wort, the Brix reading is not necessarily accurate. What is obtained is the Brix WRI (wort refraction index). Only after dividing the Brix WRI by the wort correction factor is the actual Brix known. It is helpful to know that Brix and Plato are nominally the same to 3 decimal places, so the corrected reading can be treated as Plato (°P).
The correction factor is needed because wort has a different density than sugar water which refractometers are designed for. The wort correction factor is specific to the instrument."
From a Brewers Friend article explaining their correction factor spreadsheet
By the way, don't think that I did a bunch of work changing my recipes from SG to °P, it's just a click of a button, lol