First of all I find your assertion that Indians are as much bothered or need to be bothered about the Durand Line as much as the Afghan is ridiculous.
Secondly, the basis is the same as China getting "back" Hong Kong from British. As far as I know the present day KPK was given on a lease to by AA Rahman to the brits for a century and the Afghans are wanting it back once the lease period is over. This apart from the fact the "referendum" itself was boycotted by the majority of the Pastuns and even then the vote to join Pakistan was slight 50.2%.
But Indians dont do that right ? Because Chandragupta or Ashoka did not lease out Afghanistan for 100 years to some ruler like Amir Abdul Rahman did. So apples and oranges.
I agree that Afghanistan is in absolutely no f'ing position to militarily, financially or diplomatically challenge and wrest away KPK from Pakistan but that does not take away the legality of their demand just like Pakistan believes it does not take away the legality of its demand for Kashmir even though its in no f'ing position militarily, financially or diplomatically to wrest Kashmir from India.
And no offence, regarding the question "what stops others from digging out their own old maps"..what map do you have to pull out ? Afghans have that of Ahmad Shah Abdali...Pakistan ?
Fauji, why do you think Indians will jump through the roof if and when Pak sets up posts in Jalalabad ? As I said Durand is a Pak-Afghan issue. Dont bring in India inside it. When the claim further develops and it comes from Attock to Wagah, then we will deal with it.