Yep. Not supposed to wash them. Especially with any detergent if you can help it. You are right…keeps the seasoning in it.I never wash mine. I wipe it out with a paper towel if I am just cooling meat. If there is something I am cooking that has gravy or sauce I will rinse it out then wipe down with a paper towel. I never use harsh detergent on mine. I am afraid it would strip all the good seasoning off. If I water it down I usually spray a blast of pam to protect the surface and leave the splatter screen over it with a paper towel on top. It always sits on the back burner of my stove.
I will use a little butter when I am cooking in mine for light stuff…or oil if needed for heavier cooking. One that is seasoned right doesnt need much !