In handle_player_change_government() anarchy is usually true for all players, and turns is zero for AI players. Turns is zero also for human players when anarchy has just ended the same turn. The check against multiple government changes at the same turn in case of "Quickening" (and also "RandQuick" once #43334 lands) assumes that turns value zero means that revolution has just ended. So any government change attempt from AI player is taken as an attempt of multiple changes, and prevented.
In handle_player_change_government() anarchy is usually true for all players, and turns is zero for AI players. Turns is zero also for human players when anarchy has just ended the same turn. The check against multiple government changes at the same turn in case of "Quickening" (and also "RandQuick" once #43334 lands) assumes that turns value zero means that revolution has just ended. So any government change attempt from AI player is taken as an attempt of multiple changes, and prevented.