I too have greased the cases on first firing. In my case they were the under dimensioned Norma 6.5 Japanese brass. Without the grease, the cases would show the line of pending head separation on the second firing, even though I neck sized only after the first firing. So the stretch was born on that first firing. I guess I didn't use grease, it was Imperial sizing die wax, and not a heavy coat. I got a lot more than two firings out of the sized to the chamber brass. I had a strange line working its way back on some of my Krag cases once. I'd been shooting a lot of cast Belding and Mull 311169 bullets at 1300-1400fps. Lots of fun shooting at golf balls at 100yds and hitting them pretty regular. But I thought I'd ringed the chamber or something as this line worked its way back on the cases. Turned out to be lube blowing back on the cases and gradually building up in the chamber, working its way back. I suppose it could have built up to the point that the bolt would have been taking all the pressure. Might have done some harm had I put a higher pressure reload in without cleaning the lube out first.
"I have sworn upon the Altar of God, eternity hostility upon all forms of tyranny over the minds of man." - Thomas Jefferson