This was discussed last month HERE.
The sentiment in that thread seemed to be that it is not a mistake and that Korthia catch-up gear is only intended for those that do NOT do participate in Raid, Mythic+, and rated PvP. It’s only for those folks that do LFR, heroic dungeons, and world quests. Subsequently, Blizz doesn’t want that subset of players to get ahead of those doing any/all of the primary 3 pillars of content, so it’s gated in both Archivist rep grind (Tier 6 for both 226 and 233 upgrades) AND both 226 and 233 upgrades are locked behind renown (61 and 75 respectively). That will keep those casuals from getting ahead of raiders, M+, and rated PvP players, who will already have better gear than 233 so don’t need/care about this heavy-handed rep & time-gated renown grind.
I don’t know if that sentiment is correct but it sure feels like it’s by design and not a misake.