Ronki, you brought up pre-partitioned Punjab. And thus, I was forced to utilize "undivided Punjab"---the Punjab of historical importance. The Indian state of Punjab (where it is majority Sikh) is only a fraction of the whole shebang, so to speak. It must be looked at in context of its historical importance. And yes, I am "basically saying that the Sikhs were busy fleeing to the Hindu India after hearing of the independence of Muslim Pakistan" as you put it.
Why ? Because standing at train-station platforms and seeing burning trains arrive one after the other with charred bodies can do that to people---they make people flee for their lives. And it wasn't just the Sikhs fleeing to "Hindu India"; Hindus also fled---and also Parsis and Christians and Jains. After partition, many of them came to "Hindu India"; and many of them weren't even fully welcomed by "local Punjabis" (the term, "Bhapa"---for example---is used by "local Sikhs" and "local Hindus" as an insult for Western-Punjabi Sikhs and Hindus that were not of "local", Eastern-Punjabi origin). 1947 was a horrible year. There were many issues---in Bengal/Bangladesh, Kashmir, Rajputana (heck, the Rajputs of Rajputana didn't even want to join "Hindu India"), Travancore, the Bombay Presidency, etc. In fact, Khalistan wasn't even among the top concerns of India at that time---let alone that of the Punjab and Punjabis. Back then, Punjabis were more concerned about keeping themselves safe from
other Punjabis, understandably so. It was a very horrific time; what millions of them went through.