Warning! SPOILERS about Outlander season 7, episode 2 ahead.
Jamie's story to Claire in Outlander season 7, episode 2 referenced one of the fantasy drama's longest mysteries from the Outlander pilot. The heart murmur of Roger and Brianna's daughter Mandy forcefully brought talks about time travel back to Outlander. While the logical development caused the necessary separation between Jamie and Claire in the late 1700s and Roger and Brianna's journey back to the twentieth century, it also led to an exchange between Jamie and Claire referencing a yet-to-be-explained detail from the Outlander pilot.
Jamie's ghost in Outlander season 1, episode 1 worked as an apt premonition of the journey back in time Claire was unknowingly about to embark on. However, in the seasons that followed, only another ghost ever appeared in the fantasy drama, and even in that case, Otter Tooth's ghost appeared to Claire next to the bones that once were part of his body, and the opal used to travel through time. Instead, Jamie's ghost in the Outlander pilot was seen observing Claire at the inn by Frank, and the encounter was never really explained, as it showed a younger Jamie, and Outlander clearly established Jamie not being a time traveler.
The dream Jamie described in Outlander season 7, episode 2 eerily referenced Jamie's ghost appearance in the Outlander pilot, as Claire's face was illuminated by electricity. While in his dream, Jamie saw Claire sitting at a desk writing, the Outlander pilot showed Jamie's ghost looking at Claire as she brushed her hair. However, the unmistakable feeling Jamie had that he must have been seeing Claire "in her proper time" hints at the possibility of a dream connection that let him see Claire as she was away from him in space and time, even if he was always unable to time travel as Claire and their descendants could.
This would make sense with the Outlander pilot placing Claire and Frank in Inverness during Samhain, a pagan celebration presented as brimming with magical forces in Outlander. Given how a power cut also marked the preternatural meeting, Claire and Jamie's brief connection in 1946 could have been helped by the circumstances in which Claire found herself, with the link highlighting Jamie and Claire's relationship through time. As it wasn't Claire seeing his ghost but Frank, Jamie's ghost's appearance could be ascribed to something else. Even if Jamie's dream in Outlander season 7 didn't explain his ghost in 1946, it still brought one of Outlander's longest mysteries back into focus.
Jamie sharing his odd dream with Claire wouldn't have happened without Brianna and Roger's family traveling back to the future in Outlander season 7, episode 2. Even as the Frasers and the Mackenzies weren't completely sure Jemmy and Mandy could time travel, Jamie's inability to do so lingered on every last moment between Jamie and them. After all, if things were bad, Claire, Brianna, Roger, Jemmy, and Mandy could always travel back to the future, but Jamie could have never followed, tinging everything with a bittersweet sadness. Whenever Outlander explains Jamie's ghost mystery, it will restore some hope about the heartbreaking reality of Jamie's family belonging to a different timeline.