When I picked up my boarding pass, the agent flipped through 3-5 total passes before finding mine.

So those may also have been upgrades as well.

At FCO, there was a huge line, probably 30-45 minutes at passport control. Even then, the bags were just starting to arrive after passport control and there was a big crowd around where the bags for that flight came out.

So you may be right, really packed plane.

Anyways, unexpected and pleasant surprise.