INTJs tend to be really selective with paying attention to external realities, if they cant instantly see the relevance of something, they judge it as irrelevant and wont pay any attention to it. This can speed up the process, but if this ignored thing has more fundamental and not so obvious relevance, it can lead to big mistakes. What makes this worse, is that if the theory is built on ignoring something significant(something that would wreck the theory), its hard to go back and change the whole theory because of one consistency, especially since it already makes sense(due to ignoring this important thing) and adding this thing to the theory would make the current theory to not make sense -> adding it doesent make sense. INTJs are afterall building an Ni image from the singular(but multiple) Te things.
INTJ analysis goes from defining what something is based on external realities(Te) and combining these definitions by abstracting them(removing what isnt seen as necessary) in order to figure out the relationships between these things to form an big picture view of the things seen as being connected.
INTPs on the other hand perceive the big picture and connections between things in the external world and figuring out what it is that connects these things to understand the big picture in deep level. Naturally there can be mistakes with this approach also, but its usually about missing something in the external world big picture. While looking for what it is that connects these things there is an abstraction process going on and connections that doesent make logical sense are reviewed extra carefully and disgarded if it makes more logical sense for the big picture(and the combining unknown factor, which is being analyzed).
I dont agree with this at all. For INTP the problem space is different to INTJ. For INTP the solution may be something outside the problem space, while INTJ tends to look solution only from the problem. So there is no need to change the problem space in order to find an solution outside of it or to switch the problem spaces. You need to remember that INTJs perceive external world via Se, while INTPs use Ne for that.
This currently known version of reality is the key here. INTPs only accept one version of reality, but this version of reality is unknown. INTJs on the other hand claim to know the reality, even tho its just their version of the reality, not the real reality. Reality doesent change, only the perception of it does. The perception of reality isnt same as the reality, even tho INTJs see it as so and make the judgments(and the big picture based on them) based on the perception of reality and see it as the real reality. This is why INTJ approach seems ridiculously superficial to INTP. This superficial reality really is the perception of what is and analysis what it is(in other words SeTe), INTPs can instantly see that this isnt the reality if it doesent make logical sense compared to the core issue seen by NeTi. However, when it does, its most likely something the INTP didnt think before, at least from that perspective and can be useful.