This was intended to act as a check to prevent parliament from passing constitutional amendments (which require a two-thirds majority) without the agreement of representatives from the three new states. After Singapore left Malaysia, Sabah and Sarawak were only left with 25% of the seats, as a consequence Sabah and Sarawak were not able to stop the parliament from approving laws that would encroach on the special rights granted to Sabah and Sarawak upon merger to form Malaysia.
This mechanism was designed to prevent parliament from enacting constitutional amendments (which require a two-thirds majority) without the consent of representatives from the three newly formed states. Following Singapore's departure from Malaysia, Sabah and Sarawak were left with only 25% of the seats in parliament, rendering them powerless to block laws that encroached upon their special rights granted during the merger into Malaysia.