When searching, remember, a few words are better than many
ID13-Discarded Tile Cannot Be Used in a Joker Exchange
Question: Can I use the tile I called to do a Joker Exchange?
Answer: Discarded tiles cannot be called and then used to do a joker exchange. Joker exchanges are permitted only when a player picks the natural tile from the wall or already has the natural tile in their rack.
Source: Mah Jongg Made Easy 2024, page 23, #1