Why did the computer let me declare false mahj?

[tsloper_admin]

If the Mahj button was lit up while your tiles did not form a proper Mah Jongg hand, you must be playing in Safety OFF mode. 

Safety ON mode wouldn't allow you to declare false Mahj. That's why we call it "Safety."

The game's host is the one who chooses whether the table's Safety is ON or OFF.