Actually, even before PAP implemented GRC system of elections in 1988, PAP already implemented the NCMP scheme in 1984 https://en.m.wikipedia.org/wiki/Non-constituency_Member_of_Parliament but it was probably just a decoy to the real damage to be done by the GRC scheme which would in majority benifit large incumbent political parties who already hold majority seats in parliament, especially the PAP party which would inordinately benifit from the GRC system of elections. (The GRC system allows PAP EXCO to dismiss a PAP MP from parliament by virtue of cancellation of his political party membership since such membership is a parliamentary membership requirement throughout an MP term in parliament if he was elected under such a political party banner during elections (and also absolve the GRC of undergoing by-election unless "100% of MP vacate their post" (see bottom reference))).
Embarrassed by the fact that the GRC system of elections was obscenely successful in suppression of any opposition voice in parliament (to the detriment of democracy in Singapore), the PAP subsequently started the NMP system in approx 1991, in order to dismiss criticism that Singapore Parliament was filled with sock puppet PAP MPs whose main purpose was to sing praises and promulgate PAP Cabinet policies without much thought/ question.
ACTUALLY, if PAP really wanted to represent minority political interest in parliament, then it should have since 1984, used the NCMP system to GUARANTEE a certain number of minority race MPs in parliament. Minority race citizens would then have the choice between seeing their own constituency MP (if he happens to be of different race) or their same race NCMP as they should please and have their greviences aired in parliament (rather than having to go through absent or sock puppet PAP MPs who may not feel responsible (just as minority MPs like Halimah Yacob were not replaced vz by-election not many other MPs who vacated for one reason or another)). Minority race NCMP can also use their parliamentary access to prove their worth so that they can gain the trust of Chinese (majority race) Singaporeans who would elect them as ordinary MPs just as they have elected minority race Minister's like Mr Tharman Shanmugaratnam, Mr Yacob Ibrahim and even Mr JB Jeyaretnam an opposition MP of Indian descent.
In fact, to prove that not just race were an important consideration in Singapore Parliament, main religious group leaders like Jewish Rabbi, Islamic Ustaz, Catholic Priest, Buddhist Abbot, Christian Bishop, Taoist/Hindu Priest etc may be made NMP and contribute limited ideas from their respective religious groups to ensure that all considerations from a racial/ religious/ social perspective are considered in a mature, orderly and mutually respectful manner rather than vz riots in the streets.
Minority representation could thus in 1984 be fully covered(ensured) vz the NCMP system for minority racial representation if LKY did not intend for the NCMP system to just be a decoy to distract attention from the damage to democracy in Singapore due to the 1988 implementation of GRC system of elections.
Now, a court case has revealed the worms in the GRC system of elections and how it sacrifices the trust of minority races to the dynastic and autocratic ambitions of the PAP government by shortchanging the replacement of elected MP vz by-election, even worse the case when the missing MP is of minority race, which GRC was invented in the first place to ensure; a purpose or claimed intention almost immediately forgotten.
Political vibrancy needs to be returned to Singapore and comments like the following (from AGC) only show how badly the old boys club PAP government is dragging the development of democracy in Singapore severely down:
"AGC's lawyers said that Article 39A only requires that the GRC team have a minority member at the point of elections.
They also pointed to Section 24 (2A) of the Parliamentary Elections Act, which states that in the case of a GRC, no writ shall be issued for an election to fill any vacancy, "unless all the members for that constituency have vacated their seats". "https://www.straitstimes.com/politics/court-of-appeal-hears-legal-bid-for-by-election-to-be-called-in-marsiling-yew-tee-grc