I disagree with the article's assertion that many IxFPs mistype as INFJ. I also don't see INFJs described as idealistic dreamers all that much, as that usually is given to INFPs (who get shortchanged in the description of our intellectual inclinations

). I do think that some positive traits that are ascribed to INFJs apply equally well if not more to INFPs, and I think this makes INFPs sound like "lesser INFJs" to people. Rather than being the
result of mistyping, I think it is more likely the
cause of it. What I think causes it is simply lack of real world exposure to INFJs, given they are not common or easy to access beyond their Fe exterior, and so people's imaginations end up formulating some idealized INFx hybrid.
After a decade of hanging around typology forums online, I would say the most common mistypes for INFJ are ENFJ and ISFJ. As an INFP, there is far too much Si and Fe in most INFJ forums for me to stomach. I have trouble imagining an INFP seeing themselves in that kind of atmosphere...
This is BS too:
In reality, the INFJ is much more giving than they are emotional.
Won't even detail on how incredibly selfish some INFJs can be, while simultaneously seeing themselves as "giving" because their ego won't allow self-scrutiny that uncovers deep character flaws...
Emotionality is not all about a Feeling preference, given that Feeling is rational. I'd argue that sensing and extroversion are big components of emotionality, making ESFx followed by SFs as the most typically "emotional" types. The ENFx types come across as most emotional to me of the NFs.
This article also fails to note that INFJs are frequently enneagram 4, and that will give their personality a similar flavor to many IxFPs who also are 4s, but it will make them a bit different from the INFJs who aren't 4s. INFJs may also be 9s, another common type for IxFPs. Both 4s and 9s are described as idealistic dreamers too...
In person, it has been striking to me how much less intellectually inclined INFJs are than INFPs (note - that does not mean less intelligent), and how it is harder to tell them apart from ISFJs than INFPs, unless they are e4s. They do seem more pragmatic and discerning in long-term planning, as well as more interested in "community", and that part of the article is probably the most informative for discerning between INFPs and INFJs.
I also think ENFJs mistype as ENFP more than the other way around. I am starting to think that ENFPs are just the catch-all type for any ExFx who sees themselves as a bit quirky...
And while there certainly are mistyped ENFPs among the INFP crowd, I don't think they are as common as mistyped ISFPs (a totally understandable mistype, given negative bias towards sensing types).
And neither of those are as, er, contaminating to the understanding of the type as the Si mistypes. I hear so many comments about INFPs that are describing Si, or people even referring to tertiary Si in INFPs as if it is our primary characteristic. I agree that INFPs are more contemplative and restrained than ENFPs in general, but we still will exhibit a Ne preference over a Si preference.