A few issues to consider:
Remember that relative to the rest of Punjab, and even the river valleys in parts of Afghanistan, Potohar is a rough, barren land. Its quite likely that the Aryans went around Potohar (or at least raced across it as fast as possible) to get to the more fertile and hospitable low lands between the Jhelum and Yamuna rivers. This is exactly what latter conquerors did (Turks, Afghans).
Also, there’s been a lot of population movement in northwest India across the centuries. The Jats for example, who have the highest Steppe admixture in East Punjab and Haryana, likely aren’t from that region, but migrated there from Sindh/Multan, and before that, somewhere in north/west Punjab. Just because populations are found in a certain region today, does not mean they are from that region.
Lastly, Western Punjabis seem to historically place less of an emphasis on inter-caste or inter-tribal marriage. Potoharis especially (based on Harappa data scores and records from British officials). Which means that even if groups with high Steppe existed/remained in Potohar, they would have been absorbed into the general population, and not existed as endogamous steppe-outliers (like Brahmins or Jats today).