That's what my guess is, but you would thing if the seasoning was coming off, the finiash would eventually look splotchy or something. However, the finish seems fine. There doesn't seem to be any of it missing afterwards.
I mostly use Crisco. Occasionally, I'll use lard (I bought a jar of "pure pork lard" at Sprouts). And, sometimes I will use Crisbee.
When I use Crisco, or Lard, I hear the pan for about 5-10 at 200. Then turn it up to 275 for the same amount of time. Then 350 for 15 minutes. Apply oil. Wipe off oil. Then 15 min at 425. Wipe again. Then an hour at 500.
I used to only get it up to 425, and have even played around with 350 for 90 minutes, but it doesn't seem to make what method I use.
I cook the eggs at a setting of "3". (My electric range goes from 1-10.) and I cook them in butter.
Oh well, I'll just keep using my #3. Apparently the Hover Technology prevents black spots.