They probably don't need to be tall like models (there is a lot of idols who are the "short n cute" type) and asiatic people are usually skinny... but I don't doubt they're unhealthy ╮(￣▽￣)╭
The trainees constantly say that they need to lose weigh. Aru herself hasn't eaten 3 days, as do some other girls. How is that not unhealthy?
They have to have the perfect bodies, of course they are unhealthy. Just look up TWICE, Blackpink, and any girl group. There are even boy groups that deal with this. Suga (a boy group member) is around 6 ft, weighs 130 pounds, 59 kg, and while he was streaming, he looked at his own face and said he needed to lose weight....He was already at 130 pounds. But the netizens and fans want a pretty and perfect idol...so.
I have a friend who is like 158cm and 46kg. She is not unhealthy and eats a lot but that is her body type. BUT like I said, I don't doubt that they're unhealthy pretty much because, as you said, some of these girls are starving themselves. I just think saying that "98 pounds is not healthy" is something relative.
The girls had to weigh like 98 pounds, that's ridiculously unhealthy... is this really what idol training is like?