That's correct. treasure_hunt_mode applies to the whole game.
If you use default mode, it automatically determines the end of the game for you and prints the message in the all_treasures_found_win_game system message.
If you use bespoke mode, you have to determine the end of the game yourself. That's what Adventuron was describing. This is where you get the opportunity to clear the screen and remove the status bar.
Reading back through your thread, it looks like you want to clear the screen when the game is over. It's 2:00 a.m. here, so I haven't got time to solve your problem right now, but Adventuron did describe this in the documentation thread (the one that's now locked). He gave you two methods to do this. Can you please try this and get back to me if it doesn't work. Remember that the code he gave you goes into the on_tick{} block. If it doesn't work, post the whole of your on_tick{} block here.