I had always maintained that it's was going to be one uphill task to send the Afghans back due to the fact that they do not recognize the Durrand Line. Instead, it has territorial claims on areas stretching from the Afghan-Pakistan border to the Indus River, all told comprising nearly 60 percent of Pakistani territory.
After the founding of Pakistan in 1947, Afghanistan demanded that Pashtuns living on the Pakistani side of the Durand Line be given the right to self-determination. Unsurprisingly, both Britain and Pakistan refused. In response, the Afghan government then began to ignore the Durand Line and instead assert claims over territories that lay between the line and the Indus River.
Many Afghans still dream—Pashtuns in particular—that one day they might reclaim the territories their forefathers lost between the Durand Line and the Indus River. That, of course, is unrealistic: the country lacks the political, economic and military means to pursue any such claim. At any rate, the 30 million Pakistani Pashtuns would appear to have little motivation to join the 15 million Afghan Pashtuns.
But there are those Afghans whom the OP interacted with who still think that it is an achievable dream. Why should they leave the land which they think should rightfully be theirs? Sorting this imbroglio will not be an easy task!