This topic is in Ustad video lecture:
“Zahoor” is Urdu word that mean “Zahir honaa” appearance. The birth of masoonmen (a.s) is no doubt is totally separate and not like our birth but That been said If we start calling all of our masoomen birth as Zahoor then it mean there was not real relationship as son, daughter and sister because they were just appear not born (wiladaat). It is no doubt that 14 masomeen (a.s) had zahoor in this world but their birth can not be falsified or confused as appearance. For example Imam Ali (A.s) is called Ali ibn Abi Talib mean son of Abi Talib. The re-appearance of Imam Mehdi (a.s) can be called zahoor but If we call wiladaat of masomeen as zahoor, then, what would you called shadaat of janab-e-mohsin? Then 1400 hundred years of history of sheyaan-e-ahlabait will be in question about janab-e-mohsin. Then anyone from non shia can say if they are not really born and just appear from sky then the blame of shadaat would not be valid because it was zahoor it was not in Bibi Fatima (a.s) unborn child. These point can be heard from this video.
please start the video from 36:00