I came across the following sentence in an old Language Log post
"A recent New York Times article described the Japanese profession of hostessing, which involves entertaining men at establishments where customers pay a lot to flirt and drink with young women (services that do not, as a rule, involve prostitution)."
The question being asked there is whether "as a rule" here means that there is a rule that such services can not involve prostitution or rather that ther is no rule that says it must involve prostitution.
Mark Lieberman preforms a fairly extensive dive in how "as a rule" is used currently and how it used to be used and comes to the conclusion that "as a rule" doesn't imply there exists any rules, regulation or mandates. Instead just saying how things "generally are, not how they should be or must be."
This makes sense to me in that I also see "as a rule" meaning usually or in most cases. But to me that doesn't really answer the question, which seems to be more about how one should read the negation.
Parsing the sentence best I know how, I would have a slight tendency to favor the reading, that the provision of the services does not imply that prostitution is involved, although it could be. As opposed to parsing it as though provision of the services in most cases does not involve prostitution.
For the reading where in most cases prostitution is not involved I would expect a word order of "(services that, as a rule, do not include prostitution)."
I'm not really sure if this reading is correct in general and if it's really determined in how tight the negation is bound to the action.
Can anyone explain please?