I come from a running background and your friend's marathon training looks more like how one would prepare for a 5k race. I will say that training methods should be in some way based on what you enjoy doing. Consistency is the most important factor in training and enjoying your training is more likely to keep you consistent. So personally I would try to ride a hilly 30 miles on my short days. And I would try to ride these fairly hard, particularly since I'd be interspersing rest days.