you are misinterpreting some things.
because Mo is doing X does not mean you should be doing X. YOu are not MO and have not been doing what he has been doing - have you?
Understand that just because he is now running 1 minute faster on his recovery runs does not mean his is not running easy on his recovery days...after doing many miles at a slow (fat-burning pace) a quicker pace will feel easier. for him 5:45 is easy. He also probably didn't change his pace on these runs overnight...this was a gradual process.
if you are like MO on a 4 year olympic plan you probably want to be chaning things up each year
year 1 - slow base building
year 2 - maximize milage
year 3 - begin to increase the pace & bring milage down
year 4 - add in the high quality speed work
one of the reason the slow fat burning pace is so important is it improves you effciency at all paces. and makes doing those faster workout easier on you - you can recover much quicker from them.
many runners mistaken think that after they bring their milage down and start running faster, that the key was bring down the milage...but perhaps is was first raising the milage and then bringing it down. (does that make sense?)
example - say you have been running 120-140 miles per week with a lot of slow long runs.
then you bring it down to 100+/- and you notice your race times get quicker.
What caused the improvemnt?
1) lowering your milage
2) doing the base first and then lowering your milage
to your idea of "switching from a steady diet of 10-12 milers at 7:30 pace"....first if those have been your long days - i would say switch to a steady diet of 16-20 milers at that same easy 7:30 pace if not slower (see if you can slow down to 8:00+ pace - the slower the better for now)...but also when you do 5-7 milers, 6:45 pace is not going to get you anywhere - if those are meant to be steady state or tempo runs they need to be faster than that - your should be trying to run in a zone of efficiency. for a 15:50 guy that would probably be 5:30 - 5:45....shoot for the higher/slower pace first and then gradually bring it down as you get fitter.