In The Wizard Of Oz, Dorothy’s friends all thought they were missing something.
The Scarecrow didn’t have a brain, the Tin Man lacked a heart and the Lion had no courage. Dorothy takes them to see the Wizard, thinking that a great and powerful man like him will be able to give them the qualities they lack. Ultimately though, he shows them there is nothing he can give that they didn’t already have. All he gives them are symbols that recognise what was there.
Those qualities were there because they had the opportunity to show them through their adventures. They had to do something to demonstrate their intelligence, their love, their bravery, but after years of doubt they couldn’t see they had those qualities. They had to have the symbol and someone to point it out to them.
There are two Wizards in your viva. They can’t magically give you a PhD. Their questions give you the opportunity to demonstrate what you can do, something that you’ve been doing for a long time.
The curtain is pulled back and the truth is there. There’s no magic, but that’s no problem. You already have everything you need.