I thought I'd circle back to this post. Alan makes a good point.
Race pace practice IS important as long as:
1. It's based on a realistic race pace
2. You've done the work to allow your body to abosorb that training.
3. You don't fall into the trap of thinking that if you can do X pace in a workout that you will hit it in a race and end up racing all of your workouts.
I could see a situation where your guy gets to 4 x 1600 with long rest and is unable to come close to 9:30. As a JC workout hero, I once did 5 x 1 mile all in under 5:00 but could not break 22:00 for a 4 mile CC race. None of the courses we ran were that hard, either. I also ran 5 x 1000/200 at 2:55/32 with a 200 after the 1000 and a 400 jog after the 200. I never broke 16:00 for 5k and right around the time of that workout, I ran a 3200 in 10:10, just absolutely falling apart in the second mile after coming through the first one in 4:55.
All I know is that once I started tying workout paces to an approximation of specific physiological checkpoints based on recent TT results, my teams started running way better and way more consistently. At the same time, I backed off the amount of VO2 max paced stuff in favor of more CV, Threshold, and Sub Threshold, but also including small amounts of supra maximal reps with full recovery.
For example, most recently during our Covid fall of no competition, we ran a few simulated meets breaking the team up into squads and having them compete against eachother. We spent most of the fall in an extended "summer base period" with our fastest workouts at 95% of vVO2, with the work bouts not exceeding 1:30. The faster kids did those in bouts of 400m, the slower kids in bouts of 300m to stay within the parameters. During this period, we spent most of our hard efforts on threshold type stuff. In our final TT of the fall, 6 of my top 7 boys ran lifetime PRs with my top boy dropping his PR from 11:50 as a freshman to 10:34 off of splits of 5:34/5:00. The fastest 400 he ran in training was 78.