Contrast is at the heart of humor. Many comedians use the tactic of taking completely different and disconnected topics and finding a way to combine them. Sex Advice From Grandma is definitely a feature that offers contrast.
The more exterme grandmother’s personality is, the better. If she’s high-spirited and opinionated, it can add to the show. On the other hand, if she’s well-spoken but kind and nurturing, it can be charming and endearing. Either works, as long as she isn’t boring!
It can be a bit controversial. Or, it could be charming and hilarious. It can also be a character defining feature for a cast member.