He said Virgin wanted Airbus / Boeing time because due to the lack of landing practice available on the line at Virgin, they needed candidates fully conversant with landing a jet before they joined Virgin. I remember it so well because he also said "Get all your flying out of your system before you join us, because you'll do next to none once here". Ouch!
It is true in long haul that pure flying is limited, especially as an FO when there is a lot of training going on. I remember once not sitting in the seat for T/O or landing for 6 flights.
The main reason why they want type rated/commonality is that it's costs less to train. Ex-military guys rarely have any problems flying, but now have problems getting in for the reason stated. During recent expansion Virgin favoured type rated Airbus pilots to the detriment of military guys - purely on time and cost of training. Hopefully someone will see sense and balanced workforce will ensue.