they may have lived with some relatives in mansions in Islamabad that's why they did not get the chance to see that Islamabad has a street and a Gali with the same number in the same sector. The houses in street and gali are totally different in terms of size and living standard of their occupants.
The demographics and weather of Islamabad have changed a lot. Now you witness women riding at the back of the bikes like men sit on the bike (crossed legs vs ...........) and you will find kachi basti right in the middle of few new sectors, these women and their families are definitely from Lahore or Punjab. Then there is a quite a number of prado running idiots from one specific community (that was displaced because of ops) who have no civic sense at all, they have money but lack a lot when it comes to how to live in a capital city. And finally you do get a chance to meet Karachi businessmen in markets owning different shops. Plus persian speaking Afghans they were the first one to disturb the peace of this city.
Though it cannot be compared to Karachi and Lahore due to sheer size and popultaion of those cities, however give Islamabad sometime and it will prove nothing less than those cities in terms of garbage, crowded streets and bayhungham traffic.
P.S: Faisal mosque is over rated I don't get why praying or having ones nikah in that mosque is considered more wajib ul sawab by people of Islamabad.