Their applications were not instantly approved and they received the usual "your application is being reviewed so please wait for up to 10 days" response after submitting the application.
When this happens one can call the new application department to follow up with the application, and usually AmEx will ask a few questions and then approve the application if there's nothing wrong with your credit.
However, this time when they called in to inquire about their applications status, all of them were told their applications were being reviewed by an "executive team", and the new application department phone reps cannot approve their application before the executive team finishes the review, so they need to wait a few days for a decision to be made by the executive team.
(IIRC the new application department reps used to be able to approve applications themselves.)
So they waited a few days and received phone calls from AmEx and were told their applications could be approved if they wanted but they would not be getting the welcome bonus.