One of the changes observed during Beta was that quests were awarding every appearance unlocked by them, regardless of the character's armor type/class. However, this quality-of-life change is currently not present on live servers.
However, this change was either scrapped or didn't make it for pre-patch, as completing quests is only rewarding appearances that the character can use.
Another change players hoped to be added with this system was a retroactive appearance award for quests completed pre-War Within.