Although Thurman won his comeback fight, but maybe only a few of us here might be impressed with that because his opponent is not that well known.
Before his comeback, he actually beat Barrios who’s a well-known boxer. Fundora, on the other hand, isn’t really that established, he only got popular after beating Tszyu, so he hasn’t truly been tested against a real champion yet.
No, Barrios wasn't well know that time, Barrios was also coming from a lost to Tank Davis, while Thurman was away from the ring for 30 months or so after his defeat on Pacquaio. And this is also Barrios moving up in Thurman's weight class.
Thurman hasn’t beaten a 6-footer before, but who knows, maybe he can pull it off and be like Canelo who loves taking down taller opponents. At the end of the day, it’s all about strategy and how he adjusts, because height and reach advantage don’t always guarantee a win against a shorter fighter.
I do agree that he has a puncher's chance to beat Fundora, every one and maybe the scenario that you are saying might happen as it will be a big challenge for Thurman to beat that tall of a boxer. But he should still have the mental hunger just like before as he was a unified champion at 147 lbs but then moving up another weight class.