I think dogs need a specific set of cues to convince them to pee, and as they get older that gets a lot more difficult. I'm seeing the same thing with Lily.
During the brief time we had Charlie Brown, the dog we found on the street and were keeping whilst looking for his owners, we had a simultaneously gross and uproarious repeated experience of Charlie starting to pee, Lily going to sniff at it, and getting her head peed on as she didn't wait until he was done. I don't think she ever figured that out. But yeah when people bring dogs over they go out on the deck, pee where Lily peed, then she runs out and pees right there too and then the other dog comes back and pees there again. It's terrific.