Essentially a rural west India/Afghan dress pattern.. Nothing to do with it being "Pakistani"or otherwise
The various iterations of it then came into royalty with the Mughals, eventually becoming the Kurta Pyjama which at the end of the day is a Shalwar & a Kameez or vice versa depending on how you see it.
All of them are iterations of the same basic Turkic Afghan dress which can then be extrapolated as having links to various other cultures as "their" dress.
There is nothing Pakistani or non-Pakistani about it- it is as much a part of culture as is the Kalash dress or the bangles of a Sindhi-Rajasthani woman in a thar village.
So while North Indian Hindus can claim the Kurta Pyjama as their dress, so can the Muslims because at the end it is a pass down from the amalgamation of central asian/Afghan invaders with the local culture... the same goes for all across Punjab.. wherever invading armies went, they brought their ideals which based on the time they stayed ended up being absorbed into a culture. Be it in the areas of Pakistan, India or Bengal ; this diffusion of culture took place over two thousand years.
The idea of culture is to create an amalgamation of what constitutes the entirety of individual cultural heritage rather than assign one like puritanical nazis.
Because at the end of the day, the suit worn my most Pakistani men at their Valimas has NOTHING to do with the land or culture less than a 150 years ago, but is now considered traditional to do so.