Urdu Speaking Hindustani people of Gunga Jumna culture and traditions from UP, CP started to come in Karachi from 1950 after Liaquat-Nehru pact. They did not come in Pakistan in 1947.
In a matter of fact, the Liaquat-Nehru pact was for the settlement of dislocated Punjabis due to the division of Punjab and not for the people of other areas.
Punjab was declared as agreed area and other areas were declared as Non-Agreed areas for migration, but as a prime Minister of Pakistan, Liaquat Ali Khan manipulated the agreement to settle the people of his native province in Karachi.
In 1947, only the UP, CP politicians, bureaucracy and the establishment came in Karachi, the capital of Pakistan, to take the charge of Pakistan. In 1948, the students of Darul Uloom Nadwatul Ulama, Darul Uloom Deoband and Barelvi institutions in United Province of India and the Students of Aligarh Muslim University, with their families were brought into Pakistan through special trains by declaring them the Potential Immigrants from India. They were provided the services in teaching institutions and government departments of Pakistan. Students of Aligarh Muslim University were taken as the high-rank officers in the bureaucracy and the establishment of Pakistan. In Karachi, the capital of Pakistan, to settle them, the first residential colony for them with the name of the PIB Colony was built by the Chief Minister of Sindh, Pir Illahi Bux (3 May 1948 to 4 February 1949).
In Sept 1948, first one Quota System for Pakistan was introduced by the Prime Minister Liaquat Ali Khan and it used a Regional/Provincial model for recruitment in Government Jobs and accordingly; Bengal 42%, Punjab 23%, Potential Immigrants from India 15% and Karachi had a 2% separate Quota. All Other provinces [Sindh, Balochistan, and NWFP] and the Princely States had a 17% Quota. Later in Nov 49, instead of using the term Potential immigrants from India, merit was used and the new quota was; Merit 20%, Karachi 2%, Bengal 40%, Punjab including Bahawalpur 23%. All other [Sindh, Balochistan, and NWFP] had a 15% Quota.
Three full provinces Sindh, Balochistan and NWFP were given 15% Quota and Urdu Speaking Hindustani Muhajir's alone were given 20% in the name of "Merit " and 2% for Karachi alone, that makes it 22%. Ironically, the 15% Quota of Sindh and 23% Quota of Punjab including Bahawalpur, that too normally went to Urdu Speaking Hindustani Muhajir, due to their settlement in the cities and towns of rural Sindh and the urban areas of Punjab from 1950.