So @zebratron2084 and I just sat down at Solstice. I got the password and typed it in.
"What's the password again?" they asked. And as they did, an alert popped up on my screen: "Share Solstice password with Zebratron?"
I said yes. We both felt mildly creeped out by this. Apparently our Macs have figured out that they spend enough time together that we are likely to want to share stuff like this,