One of the secrets in training is to have a group very omogeneous.
In Berlin, from my group in Iten, followed by Willy Koskei Bitok, we had the following athletes:
Amanal Petros (9) 2:04:58 (German Record) (previous 2:06:27 in 2021=
Boniface Kimutai (10) 2:05:06 PB (before joining the group 2:11:08 in 2022)
Tadesse Abraham (11) 2:05:10 World Master Record and NR (he joined the group in the winter 2021/2022, improving from his old NR of 2:06:40 in 2016)
Josphat Boit (13) 2:05:42 PB (previously 2:06:34, always in the group)
Denis Chirchir (17) 2:08:22 (had a hamstring after 30 km and had to reduce the speed. his PB is 2:07:17 this year in Hannover behind Amanal)
Jonathan Maiyo (for a test of 30 km in 1 h 28'58") (coming back after 10 years, his PB is 2:04:56 in 2012, he's in the group from the beginning of last year when started again)
Enock Onchari (resuming training from 3 weeks only after 4 months of stop for tendon's problems. in Berlin because was a must inside his contract with Li Ning) who has 2:05:47 in Seville and 4 weeks later won Wuxi with 2:07:19 (and of course injured after this... a good contract is not only more money, but how it's possible to preserve the athlete !).
Personally, with very big groups including athletes with differences in their PB of 10 min, I don't think possible to coach in the right way : too many disturbs, and normally are the weakest creating problems because a coach can't give them the same attention given to a top runner.
Instead, in this way, can be possible to prepare athletes of same level using the same program (with only little individual variations) because the period of the competition is the same.