I think there is a common misconception that INFJs and INTJs intentionally withhold information from others, when in fact, most of the time, it is that INFJs and INTJs spend a longer time to search for information and to double check if information is true.

Check the video on INFJ and INTJs secretiveness now!

Dealing with overthinking

There is however a truth that INFJs and INTJs sometimes overthink and overspeculate on information, and that they spend too long time thinking about things that they already know the answer to. It’s important to acknowledge their right to determine when they are ready to speak out, but what you can do if an INFJ or INTJ becomes stuck in the search for truth is to show trust in their process. Tell them they know what they want and tell them to trust their own judgement, but don’t pressure them to share information early.
INXJs deal with speculative and theoretical information. It is often hard to confirm or disprove what an INXJ says. Many INXJs may not speak out because they don’t trust their own answers or judgement. Others because they feel misunderstood or because they fear misleading others with false information.
Often, INFJs and INTJs that are pressured to give quick answers, will share wrong or misleading information. Many INFJs and INTJs regret speaking out early about something they were still thinking about. Some INFJs state that “Nobody will understand you, so there’s no point.”. INTJs don’t care as much about whether other people understand them. But they spend a longer time searching for proof before they say anything for sure.
INFJs speculate more about future utopias and fantasy futures, while INTJs speculate more about future economic and financial trends. For INFJs, the problem is double in relationships because they need a long time to process both their emotions, and their theories. INTJs at least tend to have a stronger grasp on their emotions. But INTJs may contrastingly struggle with making sense. For example, they are often speaking in abstract technical jargon, that can be difficult for others to grasp. Often, the key thumb rule is to trust your process and to let your thoughts take the time they need.