They probably called them "booster" medals because trait medals say "BOOSTED" on them when you pull them. It is worth noting that "BOOSTED" on a non-trait medal gives it additional stats, but for some reason all trait medals say "BOOSTED" in pulls despite not being useful for anything but giving traits to the medal they match.
This is a great point! Thank you for pointing it out!
Boosted Medals means they get additional Strength. Usually it’s +1000 but maybe it’s sometimes more than that now? I’m not 100% sure. But all the grey medals (trait medals) are boosted automatically, which is stupid and confusing.
Thank you for the help on that one, kind stranger! ^_^