As we see there are 2 meanings of “so-called” that can be confused or misinterpreted, of which one implies falsehood and the other doesn’t.
One. to show that something or someone is commonly designated by the name or term specified.
“Western Countries belonging to the so-called Paris club”
Two. used to express one’s view that such a name or term is inappropriate.
“she could trust him more than any of her so-called friends”
Since so-called I feel is very often used to suggest that a title for something describes a meaning that isn’t necessarily accurate, what’s another term that simply expresses that something is titled something without judgment of the title?
The problem here, linguistically, is that any phrase which means this will take on the meaning of falsehood automatically, over time. It's the same way that any respectable word that means "has a disability" eventually comes to be an insult and then a slur.
If you want to say something like that, the word "putative" is still pretty unfettered by negative connotations, but only because few people use it. If it were in common use, it would follow the same path as "so-called". A more reliable approach in the long-term is to say what you mean using more words instead of fewer:
It's actually the length and awkwardness of the sentence structure that makes it resistant to misinterpretation.
I agree, even if you use another word like alleged, the word is in the sentence strictly to draw attention to the fact that the following information is of questionable validity, so by nature casts suspicion and distrust, even if the intent for the distrust is protective of the audience in a positive fashion.
So you're saying verbosity allows for more exactness of meaning, at the expense of the convenient efficiency of expecting inference to be employed by the recipient(s) of the message(s)?
You're right, but the "so-called" only becomes suspicious when it's included unnecessarily.
From OPs example if you just omit it the sentence is fine and doesn't imply that the friends are not actually friends.
In the first type of usage, "so-called" provides information that the reader is unaware of, so it's use does not imply the name is inappropriate.
In the second type of usage it's presumed the reader already knows the name, inserting "so-called" emphasises that the subject has whatever name.