On the history of Pashtun women I have a very interesting contribution to make:
An officer of the Imperial British army, recorded in his autobiography that Afghan women in the North-West Frontier Province of British India used an execution method involving urine.
Pathan women urinated into the open mouths of British soldiers who were fastened with restraints to the ground and their mouths held open with a stick.
Bugles and a Tiger (Autobiography) - John Masters:
Kyber, British India's North West Frontier: The Story of an Imperial Migraine - Charles Miller:
John Masters: A Regimented Life - John Masters:
The Savage Frontier: A History of the Anglo-Afghan Wars - Donald-Sydney Richards:
Take such stories with a pinch of salt. British writers during colonial times would make up all sorts of fables about people they conquered or were trying to conquer, to portray them as vicious lowlife savages who hadn't been touched by their glorious christian civilization. This was a tool to perpetuate their notion of the "white man's burden". Unless such events are documented in proper historic writings from contemporary times, as opposed to autobiographies and personal accounts of British colonizers, don't attach much weight to it.
Another way to measure credibility would be to find out if Pashtuns from that region have any such written or even orally transmitted stories about this. Does any Pashtun source record such a form of execution? Does it seem likely to you that a Pashtun tribal woman from NWFP/Afghanistan in the 18th century would pull down her pants (or shalwar or whatever) in front of the prisoners and executioners and pee?
Maybe it used to happen, but I will not believe it unless corroboration from local sources is found.