Not sure what the intentions were behind this change, but during beta they modified the language to drop all other sources other than costume quests => 🧪 Early Information on Costumes (Formerly Skins) [Part of The Beta Beat v23, v24 & v25] - #994 by zephyr1
My 2c on the subject, assuming that quests are only sources or they’ll be added to Titan/chest/MV are both assumptions at the end of the day. Better to ask staff and designers on their future plans IMO.
AFAIK, facts are we are currently limited to 6 keys/no and that is too low, making grind painful without gems.