The "hide sensitive content" message is just the generic message you get when you don't want the content included in the notification. It's easy enough to turn on and less easy to change once you've made that the default. And, it's a global setting, so it applied to all messenger notifications. You can't pick and choose.
The could have made it a more accurate description like "I don't need to see what you had for lunch" or "so many cat memes, so little bandwidth" but they chose to make it sound like everybody's hiding something.