Good of you to come back and question what I advised.
Let me explain it a bit, and then I'll offer an example.
The reason I would (initially) slow down your easy running is to get it under control. If we tested you today at your normal "easy" pace, we can be pretty sure that it will not be as aerobic as it should be. We could lactate test this and prove it in 30 mins.
So, I would get you to run at a more fully aerobic pace (the 7.30m/m) to start, and then, once your body adapted to that pace, I would slowly increase this pace (while still keeping it fully aerobic). In time you would get back to your 6.20m/m, but you would THEN be running it differently, using your aerobic energy system entirely, and not a mix of aerobic/anaerobic as at present. This is the whole foundation of Lydiard-based training and would not take too long to achieve.
Let's look at the example:
I had a young guy come to me with a 8.50 / 3000m PR. He came because his improvement had stalled. Ran about 50-60mpw, with all his "easy" running something like yours, 6.00-6.30m/m. As with you, I told him this was too fast, but unlike with you, I could prove it to him with a HRM (at 150 HR he was WALKING, he had to push it to 170 just to MOVE at any kind of pace?his 6.00m/m was 180 and climbing...). I also gave him a lactate test and a lecture on sport science (basically the gist of all my recent posts, all this over the first few weeks together).
He absolutely HATED running at 7.30m/m and a steady 150-155 HR (he even ran in the evening in back country roads so none of his buddies would see him), but stuck with it because he had seen my success with other runners, and was able to talk to them and get the reassurance that they had gone through much the same process. In a few months we got his "easy" pace up to 6.40 and he relaxed a bit as he saw that it was working and it was no longer so embarrassing.
Within nine months he moved his 3,000m PR from 8.50 to under 8.30.
Now, about your competitive NCAA runner. I hope you can now understand that (if he has been trained well over a number of years) he might be very comfortable at 6.00m/m. Basically just well-trained aerobic running. Paula runs this pace a lot too. But do you believe it is as hard for her as it is for you? I would expect to find that her HR would be around 155bpm or so.
But obviously your NCAA runner and Paula run at that pace NOW. Neither of them started out at that pace but, with steady work over the years they improved their aerobic ability to where they can run this pace with low HR and low (under 1.5mM) lactate (showing the anaerobic system is "quiet").
I have absolutely no doubt you can run 80% of your 60 mile weeks at 6.20m/m. But is it the right thing for you to do? Both now, and for your longterm development.
Here's a quick test to see if it is the right thing to do: if your HR at this pace is higher than a STEADY 155 bpm the whole way, it isn't.