It's not just about "crowded conditions." Think about all the things each individual needs to do every single day:
1. Wash their hands (COVID)
2. Clean themselves -- shower or bath, washcloth bathing at a sink, whatever ...
3. Brush their teeth
4. Meals
5. Use the toilet
6. Get a little exercise -- walk, stretch, move about
7. Change into clean clothes (no privacy)
8. Medical checkups and treatments
It's reported that most of the "kids" (many are 16+) are being kept in these holding rooms for days until they are processed.
Seems like there would need to be a constant stream of kids moving between toilet, shower, medical, exercise and sleeping facilities. So, it's not just about being packed in like sardines..