If it's strong Si, then for an INTP with AS, this will not only be strong as it is ("tertiary temptation"), but will look even stronger because of that "concrete" focus.
Continuing to reflect on this stuff, I also think part of the problem is thinking of the functions as things we "use". Fe isn't really "picking up social cues". That's a single trait, that may stem from a functional perspective, but is not exclusive to one. (It can come with Se or even Si as well).
So what you said is correct; it's a focus on "relationships between people".
And then "not
picking up social cues" is also likely a trait, that occurs in AS, but is not necessarily a defining factor. It just happens that most Aspies are NT's, so their lack of certain S and F skills becomes magnified. AS is essentially a sensory overload that will play out that way for NT's (like emotions are a form of sensation, so as Aspies often report, they feel overwhelmed by them; and thus T will feel like a much "safer" realm for them). I guess SF Aspies might be able to handle the emotions better, but have other problems, and probably find themselves in a bind with S activities; having trouble processing the data (like physical stuff), but nevertheless be more willing to keep trying; or at least find some other way to handle S data.