That is cos most Pakistanis even Urdu speaking ones don't really speak Urdu. We just think we do.
We really speak something called "Hindustani" mixed up with Punjabi/Pukhto/Sindhi etc etc...
You know I am in Rawalpindi right now and when I go out and about to the Bazzars I try and speak Urdu as fully as I can (I am not that good but getting better), the times shopkeepers don't understand Urdu words and then I have to use English words and they get it.
What Dr Israr Ahmed spoke in his lectures and what the FM spoke at the UNGA was Urdu. And not sophisticated Urdu, just Urdu as by definition Urdu is sophisticated.
But you are right many Urdu words are Persian words.
So how come hardly any Pakistani speaks Persian?