you're watching too much porn

No, "cum" here means that it is two things at the same time, like "a study-cum-bedroom" or a "journalist-cum-teacher"

It's not a typo. It's a preposition describing the relationship between two things. It doesn't only mean ...🙂

Oh wow. I've never heard of that. Is it a British English thing? I'm American.

It's a Latin preposition and rarely used in American English. Example: when someone graduates with honors it is used with "*** laude" or "summa *** laude" which means with the highest distinction).