That's a well done scamI've checked every nook and cranny i could find about their accounts but both of them have nothing, i can't think of anyone who would keep the same username for 15 years as well SteamREP has a page about this so it seems to be known alreadyhttps://forums.steamrep.com/pages/about-item-checking-scam/
Steam lets you clear your name history, which is pretty stupid for this exact reason. They must have phished somebody's account or guessed the password on an inactive old one.