No, that’s not true that many more did.many more didn’t. Even some of those you named. What did Sakhanovich, Shelepen, Pitkeev and Tsurskaya achieved at the senior level?
If we count how many brilliant juniors didnt achieve much at senior level...
Lets take 2014-15 JGPF, for example:
Qualifiers in men:
Jin Boyang - Successful at seniors
Shoma Uno - Successful at seniors
Alexander Petrov - 8th at euros, best GP placement 6th.
Lee June-hyoung - not a single medal at seniors, best 14th at 4cc and 24th at Worlds
Sota Yamamoto - pretty much no senior results (injury?)
Roman Sadovsky - best senior achievement: 10th at SA
Out of the 6 boys who qualified for GPF that year, only 2 are doing well
Qualifiers in ladies:
Serafima Sakhanovich - no senior results, can barely get a GP
Medvedeva - Successful at seniors
Wakaba Higuchi - World silver
Maria Sotskova - GPF final silver, 8th at worlds
Yuka Nagai - bombed everything at 16-17, didnt skate this year
Miyu Nakashio - i1th at her only GP.
Out of the 6 ladies who qualified, only 3 are doing well.
I would say that the chances of transitioning successfully to seniors are between 30% and 50%, on average.
Most skaters don't make it, regardless of the coach. Eteri is not alone here.