Yep, they refer patched IMEIs phone with 'PTA' and the legally approved ones as 'Officially PTA Approved' ones, idk, why not just say Non-PTA.
Since you have highlighted this PTA issue, another user once reported similar experience that he mistook patched IMEI phone as legal one and bought from them. There are cases like these but rare mostly because consumer did not pay much attention.
So, no matter how honest shopkeepers are or known to be, just be vigilant when buying in 'Islamic Republic of Pakistan'. 