I may be wrong about that being one of the benefits of an XBM, but then I don't understand how applying for 2 Chase cards and 2 Amex card within 4 seconds helps? Each app will see the pulls of whichever apps pull before it.
Anytime you do a 3/bm you get 3 pulls, it's just that they later get merged by the bureau if all in the same day.
The only benefit being is in the long run, that you don't have 3 pulls..
It is my understanding, that if apps are done within a few seconds, you have a better chance multi instant approvals, as the first approval is not yet in the 'system'...