As part of an unrelated question on when the X-list officially came about, I stumbled onto the
Wiki's X-list page and saw the two links for the Expanded X-/R- lists at the bottom. It appears that when Decipher decided to start rotating out sets for Standard, they held a vote for what the Expanded lists should be. Everything on the Standard X-list at that time was voted on by casual players, pro players, and internal testers. The three groups were averaged as a whole and then each group's average was averaged (so individual casual players votes were worth less than an individual tester, but all players' votes were worth the same as all testers'). They also said this:
"When a new card is added to the Standard Format X-list, the DGMA will once again ask the player community about whether the card should be on the Expanded Format X-list or the Expanded Format Restricted List. In this way, the Expanded Format will continue to be a player driven format."
Yet as time went on and cards were added to the Standard X-list, the Expanded lists remained unchanged. The exception was to add
Orkish Smith and
Strange-looking Men to them, and while I don't know why they were added and others weren't I'm willing to bet there was no community vote on them. My guess? Decipher's infamous financial woes either lost the job dedicated to keeping up with Expanded or caused that person to take on too many other things to organize a vote. They
might have announced a change in how Expanded was being managed, but I think "oversight" is the answer here.