First of all I welcome you to this forum, may your journey in this forum be happy. However, I don't know much about the topic you have raised, as I am also some new new in this forum, I have only been here for a month.
Like you, I have mobile user badges on my profile, but mainly I work on PC. I only opened my account on mobile when I opened it, that's why my profile is showing mobile user badges. You also post on mobile so mobile user badges appear on your profile, but I don't know much about how they identify this.