Your initial comment was that it doesn't seem necessarily related to socionics - this is mistaken simply because, it is related to socionics, and to issues with ethics (primarily Fe but also Fi) in general.
Fe is about self-expression and communication of feelings, thoughts, and desires, so it is naturally linked to getting to know a person. Fi has to do with more purely "inner" qualities.
Is it easier to get to know people who have a certain relationship with you? Sure, but that wasn't the question, not to mention that it's less significant overall. A Delta will still probably find it relatively easy to get to know an EIE compared to an SLI, even if the relationship is overall less pleasant. I find SLEs and SEEs pretty easy to get to know compared to SLIs, even though the relationship is more difficult.
Social introversion is definitely correlated with socionic introversion, so you got that right. But IEIs are also much more approachable than Fe-4 types.
If you want to know what I think about Reinin dichotomies you can read here