Pathan is simply the Urdu (and related languages) word for Pashtun just as German is the English word for Deutsch.
Why do our people like to propogate basless theories, fables and lies?
Pathan is also a Zaat (caste/tribe) label for Urdudans and Punjabis of Pashtun origin, but these people have no desire to be associated with the Pashtun ethnicity anymore, when they describe themselves as Pathan they mean it as a group within Punjabis or Urdudans rather than ethnic Pashtuns.