Most Helpful Guy
By that he could also mean he has social media that he made for the sake of making one that he never updated or used.
I'm in the same boat to be honest. I have an old Facebook that I made in middle school and a twitter. But I never ever put anything on them or updated anything, it was just a different way to communicate with friends at a younger age. I stopped using them partway into high school as all you see are random posts by acquaintances about them doing something random, sports moments, vines/funny videos, food tutorials, and videos of amazing people/children in the world and the most prominent of all; fake news.
He could just be using programs like Skype/Discord or any similar alternatives to communicate with a close friend group.
As for the trust issue, it has nothing to do with whether he has a social media account or not and everything to do with how he behaves and how reliable he can be.
Most Helpful Girl
I don't see why that's a big deal. I'm not that active on social media to the point of pretty much being none. No twitter or instagram. Haven't been on Facebook in months. What about not having social media makes someone untrustworthy? I can understand if it comes with other red flags like someone always hiding their phone or lying about things they're doing, but by itself it's not that weird.