Considering the explicit distinction drawn between getting paid on a week basis, where "months aren't all the same", and getting paid on a month basis, where they are, of course that's what I'm talking about. If you get paid twice a month, your income is the same every month.

While they're technically different, they're "close enough for government work", and I don't know anyone who would make the distinction in casual conversation. IMO, there's no "of course" about it; a comparable situation would be interpreting "literally", "begs the question", "ironic", and such using their dictionary definitions, when it seems clear that the writing has a more colloquial tone.

In response to the comment "when you're paid biweekly, not all months are the same", then yes, it is blindingly obvious that the current context draws a distinction between being paid biweekly, such that not all months are the same, and being paid semimonthly, such that all months are in fact the same.

You're reading the comment differently than I am. That's all I can say.