My husband's Team Frank, as are a few of the guys I know of who at the very least started out watching this to humor their wives/partners. He find it highly convenient that Claire gets to have a husband in each time period who nonetheless can never also travel to face each other. That Frank gamely stiff upper lips it through Claire showing back up after a nearly three-year absence with someone else's kid and what has to sound like a highly far-fetched story about her One True Love that isn't him to raise that child also goes a pretty long way, I think. He hasn't read the books and doesn't particularly care beyond that. Luckily, most of his takes on this series are pretty funny and the ones that aren't really aren't worth arguing about.
Even coming in the same book as the Great Misunderstanding, this just kind of boggles. Well, gee, I could maybe leave her a letter if I'm not inclined to just come out and tell her the truth like a normal person. Or, or I could have an entirely third party plant a fake gravestone in some out of the way place on the off chance she sees it and then the same woman who's never shown much interest in the history that I've made my life's work will surely deduce what it means and set off on a historical discovery tour of a country she doesn't live in with yet another third party. Why, that's perfectly logical and not convoluted or flat out insane at all.
All that said, I do kind of enjoy Jamie's very dry reaction to all of this. But really, what can he even say at that point? Frank's dead in both timelines and has gotten his final word in.