They definitely did it at faster than 5K pace effort-wise due to the grass.
Based on his other times, it seems Nico is probably in something like 13:50 - 14:04 shape (2:46 - 2:49 pace on a track). 13:50 assumes he has improved a bit from last track season to now. 14:04 is the equivalent of his 8:40 3200m at Arcadia. He did 7x2:46 on wet grass. I gotta think that's worth something like 2:42-3ish on a track, which would be 13:30-35 pace. Nico is a phenom, but I don't think he's a 13:30 runner yet.
Assume that he's improved from that 8:40 at Arcadia, which would be 2:43/KM. If he's in 8:35 shape, that's 2:41/KM. If he's in Verzbicas NR shape, that's 2:39 shape. So the workout seems slightly too hard for him. But that's not as big a concern as the guys behind him. He's a generational talent and he'll be fine if he gets good coaching in college. Jace Aschbrenner was finishing those reps like 5 seconds behind Young. Do you think he is a 14:00 - 14:20 5K runner? I do not. Brosnan probably wishes he had pulled the kid before the last rep.
There can be no reasonable debate that for 1500 - 5000 runners around this age, VO2 max work will get your kids into great shape quickly. The issue is that there is a lot less room to develop VO2 max than there is to develop aerobic capacity through LT work. All of the "powerhouse" HS programs use VO2 max workouts to get kids into shape quickly. The concern is that they risk injury, overtraining, burnout, unrealistic expectations of improvement, etc. on workouts that science has proven has significantly diminished returns over time.