No offence, but I think you took a wrong example there. Punjabi Sufis like Baba Bulle Shah and Baba Farid composed their poems and couplets in Punjabi.
And I guess the birth-place of Urdu might have been Delhi and Lucknow but the current home can be decided by the number of people who count Urdu as their first language. Another metric, could be the number and volume of Urdu literature produced. Any data or stats on this?
A lot of Sufi poets did write Urdu poetry as well along with Punjabi. Besides, it's not just people like Bulle Shah: there are other people such as Muhammad Iqbal, Faiz Ahmed Faiz, Majeed Amjad, Ahmad Nadeem Qasimi, Faraz, Nasim, Tilok Chand Mehroom, Noon Meem Rashid, Meeraji, Gul Khan Nasir, Zamir Jafri, Jagannath Azad, Aurangzeb Khan, Jalandhari. These poets had nothing to with Punjabi, they were pure Urdu poets born in the region now called Pakistan.
And other than that, there are some linguists who believe Lahore was the birthplace of Urdu, not Lucknow or Delhi. I just read this paper written by an white British author who gave substantial proof to support his claim. To me, it doesn't really matter where Urdu was born, whether it is in Lahore or Delhi. They were all the Indian subcontinent once. Like I said, Pakistan is the birthplace of Sikhism as well, but they don't claim to be the Mecca of Sikhism.