What's the purpose of a 'soft launch'?

So me (M16) and my girlfriend (F15) have been together for 2 months, we go on dates every weekend and spend time together, but I don't have a phone and she never really uses it around me. Yesterday she posted a picture of us together (w/o showing my face) and called it a soft launch. I assume it's like saying 'hey look, I have a boyfriend' to her friends but I don't understand the purpose of it? Can somebody explain?