Feels very rushed for a romantic relationship.
The mental age gap is super weird, he's 70+ mentally, she's like 18-20. Doesn't matter that's he's physically still the same, he has 70 years of life experiences, that causes the weirdness, they are just so different mentally.
She's been indoctrinated on top of that so she's not even a worldly or mature 20, she's an emotionally stunted 20.
Feels odd shoehorning in a romance this late in the game, a romantic relationship should paint them as equals and this show has been about Jack from the beginning. Putting someone else at an equal level to him right at the end feels wrong.
I personally like the teacher/student relationship much more as it sidesteps all of these issues. Being a student isn't as important as a romantic partner so there's less rush and less importance placed on her. There's no out of proportion romantic power dynamic of a 70 year old with a 20 year old. Her lacking in knowledge of the outside world is a reason to become a student rather than a reason to not enter into a relationship with her. Just works better in my eyes.