You probably got it in a daily. Everything is unlocked in dailies. There's a lot of discussion on the subreddit about how to unlock. A few claims of having done it, but they go silent when asked for a screen cap.
I'm in a similar boat. But I know I got them filled in by missingno. Which can give you items you haven't unlocked yet.
I'm not sure that is even necessary to get it to get 100000%. Real platinum God will unlock as soon as you have all the rebirth achievements, so booster pack ones may not be necessary. The DLC has only just been out 31 days so few people will have the dedication one. I'm on a four steak for dailies, so I'm not going to play today's, but I'm pretty close to 31. So I'll know the truth soon.