As shown here (text element is $mi(state)$ ) it returns pause when playing and playing when music is stopped.
Preview in editor is correct.
My phone is Xiaomi MI9 with stock rom and launcher.
Update: it does the same thing in Nova Launcher
Got another phone with MIUI of a slightly different flavor (POCO M3)
Does the same thing in KLWP and KWGT in Nova and stock launcher
States are right in editor, reversed in launcher