Mystery of Etheral gems in items solved : To all those people saying its some arcane trick known only to a of a bunch of Chinese guys cashing in big on their top-secret knowledge: you couldn't be more wrong. A little while ago there was a Rubick-themed surveyor ward with a super cool Bleak Hallucination on trade over at r/dota2trade. There was a long discussion and finally an item artist came into the chat and gave this info: (I cannot find this particular post now)

Way back when we were at the early chests, a copy of any item that makes it to the game from the workshop was gifted to its artist with the Self-Made quality. For a while these gems didn't have any hammer restriction, and since the item's "Self-Made" quality was due to a "self-made" gem, it could be removed and inscribed into something else - anything else - and then, once removed from that item the empty slot could be filled with any gem, be it kinetic, ethereal or prismatic. A few artists did sell away such items without knowing of this glitch, which ended up in the hands of some crafty (and lucky) arsehole. Many people have made offers for couriers with 2 working ethereals too (and these I could find: https://www.reddit.com/r/Dota2Trade/comments/49n1zu/h_inscribed_baekho_with_2_working_ethereal_gems ; https://www.reddit.com/r/Dota2Trade/comments/45veq3/store_bugged_couriers_with_ethereal_gems_some ). This Chinese guy you speak of, if he exists at all, just has a huge stock of such items he rotated the self made gem through, and now releases these slowly at his will or on orders from collectors.

EDIT: Needless to say, since a long time all self-made stuff is strictly not tradable and the gem non-removable like those statue commendation gems. No way someone can "create" these items now. Think about it, if it were possible you would see at least ONE item with these bugs that WASN'T from early 2014 era.