After reading this thread and doing my own observations, I'm wondering why I even bought a refractometer.
I just measured FG of a beer using both a hydrometer and refractometer before kegging, and here are the results:
Hydrometer OG: 1.060
Refractometer: 14.7
Hydrometer FG: 1.020
Est. ABV: 5.25%
Refractometer FG: 8.1
Estimated adjusted SG: 1.015
Est. ABV: 5.91%
A difference of 5 gravity points / 0.66%ABV seems like a lot to me. I checked these numbers against multiple online calculators and all yielded similar results. I guess I should stick with the hydrometer readings.
Oh well, it's a neat toy, but I'm not sure how useful it will be. I guess I can still use it to double check SG readings during mashes and post-boil, but it doesn't seem great for FG readings.
I was really hoping for it to replace my hydrometer, as I have a tendency to break them and they are less convenient, but that seems like a pipe dream now.