Lost Primarch Held on Terra New 40 K Lore

From the new Adeptus Custodes codex, we have a passage that mentions prisoners held in the Dark Vaults on Terra, one of the beings is SUBJECT XI, is this GW teasing us that maybe one of the Lost Primarchs is actually be held on Terra Thank you for watching my video, glory to the Emperor and the Imperium of Mankind Join this channel to get access to perks: YT MEMBERSHIP DISCORD TWITTER FACEBOOK INSTAGRAM ELEMENT GAMES OVERLCOCKERS MERCH PATREON