Calling gold guest list it’s exec club number and name, then the 3 security questions, first two are always email address, billing address and then the final security question seems to randomly be either passport number, last 4 digits and expiry date of saved card, am I travelling alone and very occasionally a nominee on the account.

I presume once you’d answered 3, the agent mistakenly carried on through the list and when you declined to answer the additional extra question about your passport number they realised they had checked enough so they could carry on with your query.