My understanding (and this may be hoop!) is that the accelerated promotion offered to graduates means that they will become a flt lt at the same age as someone who joined from school (this does not take into account gap years etc). Further advancement is based on merit. With current government policy encouraging half of schoolleavers to go to university and post graduate salaries in excess of IOT cadet starting pay, something has to be done to encourage graduates. Whether or not this should be branch dependant is another matter.
I still think that the high calibre refers to the individual rather than the quality of their degree (grade or subject!)
Duncs