The Punjab of 1901 held more than the language of Amritsar and Lahore. Saraiki was spoken across Multan, Bahawalpur, Muzaffargarh and the Derajat. Hindko was spoken at Peshawar and in Hazara. Pothohari was spoken in the north.
Whether Saraiki is a dialect of Punjabi or a separate language is a live political question in Pakistan, tied to a long-running demand for a separate Saraiki province out of southern Punjab. The 2017 census recorded Saraiki separately.
That question is the mirror image of the argument in Indian Punjab in the 1950s about whether Punjabi and Hindi were distinct, which was settled politically rather than linguistically.
A language boundary in this region has never been a linguistic fact alone. Where a dialect chain is cut, and what the pieces are called, follows what people want the boundary to do.
Bahawalpur and Multan carry a literature, a music and a Sufi tradition of their own, and Punjab's history as usually told from Amritsar or Lahore leaves out about a third of the province.
It has its own script conventions, its own Sufi poets, Khwaja Ghulam Farid above all, and its own literary societies, and it has been counted separately in the Pakistani census since 1981. Whatever the linguists conclude, an official form that offers it as a box to tick has already settled the matter in practice.
The demand for a southern Punjab province is carried in Saraiki, and the argument is about the concentration of the province's resources in the central districts.
Hindko in Hazara and Pothohari in Rawalpindi are the northern equivalents. Punjab as a province contains at least four things that could be called separate languages if their speakers wanted them to be.