It's annoying. There's a mismatch between what's shown in my Steam library tab's DLC listing for CK II, EU IV, HoI IV and Stellaris. For example, like you I pre-ordered the Stellaris Galaxy Edition, the library tab shows it, along with the ringtones, soundtrack, etc, yet the Steam store page lists the soundtrack, ebook and upgrade packs as not in my library. Same for EU IV, I own everything available in the e.g. Early Upgrade Pack but the pack itself isn't shown as owned on the store page. Same deal with CK II and HoI IV.
Looking at SteamDB's listing for Stellaris alone just gives me a headache trying to tie things together. Would be nice if Paradox/Steam could sort it but I'll still survive if they don't.