Warning! SPOILERS about Outlander season 7, episode 5 and the Outlander books ahead.Jamie's worry that Fort Ticonderoga would have been expunged was prompted by learning about Simon Fraser of Balnain fighting for the English as a Brigadier-General under John Burgoyne in Outlander season 7, episode 5. The end of Outlander season 7, episode 5 proved Jamie right about the fort's weaknesses and how a Highlander would think to use the terrain to their advantage. However, the episode also introduced a relative of Jamie that is central to the story of An Echo in the Bone, Outlander's seventh book on which season 7 is based, even if his side of the family wasn't really introduced before in Outlander.
The American Revolution already left Jamie and Claire in a pickle because they knew who would have won it and because Jamie's biological son William Ransom was happily willing to fight for the English. Simon Fraser of Balnain also fighting for the English not only added another person related to Jamie whom he could have met on the battlefield but also meant that someone who knew how to use the environment to his advantage fought against the Continental Army. Although Simon Fraser caused the Continental Army problems at the end of Outlander season 7, episode 5, he will also be instrumental to the furthering of Jamie and Claire's story.
Jamie telling Claire who Simon Fraser of Balnain was in Outlander season 7, episode 5 made a point to explain how it wasn't the "Old Fox you met or his son," referring to Jamie's famous grandfather that was introduced in Outlander season 2, episode 8, "The Fox's Lair." Jamie's grandfather Simon Fraser, 11th Lord of Lovat, is the link between Outlander's fictitious story and the Scottish real history, and it's through him that the connection of Simon Fraser of Balnain to Jamie can be explained. The real Simon Fraser, 11th Lord of Lovat, was the son of Thomas Fraser of Beaufort, 10th Lord of Lovat, who had Hugh Fraser as a brother, among many others.
Jamie introducing Simon Fraser of Balnain as a second cousin, son of Alexander Fraser of Balnain, mixes once again Outlander's fiction with Scottish history, as the history of Clan Fraser of Balnain explains the Frasers of Balnain as having received lands from a Lord Lovat named Hugh. Hugh Fraser of Balnain received the lands from Hugh of Lovat and had as a son Alexander Fraser of Balnain, whose son was Simon Fraser of Balnain. This way, Outlander season 7 explains Jamie's connection to his second cousin through the Old Fox himself, Simon Fraser, Lord of Lovat, and his father, Thomas Fraser of Beaufort.
Outlander season 7 stopped Jamie, Claire, and young Ian's trip to Scotland because Cornelius Harnett conscripted Jamie to fight at Fort Ticonderoga. However, Simon Fraser of Balnain is the key to continuing their journey back to Scotland in An Echo in the Bone, Outlander's seventh book. Simon's fatal wound during the second battle of Saratoga makes it possible for Jamie and Claire to visit him under a flag of truce in the book.
Jamie and Claire's trip to Scotland is only sped up because Jamie wants to bring Simon's body back to Scotland so that his family can bury him. Considering how the second battle of Saratoga also has Jamie narrowly missing shooting William in the head, Simon Fraser of Balnain's death in the seventh Outlander book proves the only way Jamie could distance himself from the battle, trying to keep his promise not to be on the opposite side of his son on a battlefield. Hopefully, in furthering this story, Outlander season 7 will soon let Jamie and Claire on their way to Scotland.