Of course, for 12 and 10 , substitute 10 and 8! 12 and 10 includes the X12!
Which of course means that cutting the hourly total number of 21s down to 6 would make even less sense, as they'd lose 20% of the existing total capacity. And frequent services often get the passenger numbers that they do because they are frequent. As soon as popping out of the house and hopping straight onto bus becomes less of a likelihood, the bus becomes less attractive.
RE: Go North East: Upcoming Service Changes