You are right. It is used in Singapore to keep the people' obedience and make sure they know their place and OB markers.
Outside Singapore,
I have succeed in challenging unfair contractual terms in a law of court.
There are limits, eg unfair financial contracts cannot be challenged.
Just thatyou need a proper court, proper justice system - not the type run in Singapore.
I am not supporting the PRC, they should have formed their own union and negotiate with management for better pay.
But of course, both Singapore and China do not have envious records of managing industrial disputes.
O$P$ contracts I like best.