Actually not oral history, Akhund Darweza of Akbar times has written about Khan Gaju. He had united entire Khashi confederation under his banner and his territories extended from Nangarhar to Margalla and from Kafiristan to Kalabagh, it was a loose tribal confederation and the rule over the region was not proper. He led military expeditions into Hazara, attock and Ghakkar territories and extracted tribute from them. It seems Ghakkars agreed to pay tribute , while kept their Independence.
Mughals were no Persian Kings, if i remember correctly Babur defeated Ghakkars in a battle, there was no outright allegiance to the invader. Before Babur, Ghakkars were allied to Lodhi Afghans as mentioned in Baburnama. The opposition to sher Shah was due to sticking to alliance with Mughals, not due to his ethnicity.