Actually Ni is the function most linked to foreseeing the future. Ne is about possibilities in general. Ns tend to be more future focussed, but NJs are the best at it.Future possibilities is a Ne thing which xSTJs possess.
Who is making assumptions about types now? Boromir is not manipulative - he's far too direct for it to be so. He lies and tries to persuade Frodo to give him the ring - which any type could do. The ring creates a desperation in people that would affect all types. Boromir just had more of a need (ie. to save his people) so he was more susceptible. And Te doms are more inclined to be volatile (not always but often).
I can't watch videos at the moment, so I can't look at these clips.
This could be true of any introverted type.Aragorn is very emotionally reserved - like in this scene, he takes Boromir's anger at him, until finally his emotions lash out at Boromir - that's usually an Fi thing more than Fe: https://www.youtube.com/watch?v=IcYPWM5ukU8
All this is besides the point and is a total derail from the topic, anyway.