Ahem, read part (ii) again. If a parent is a arrested while accompanying a child - what does that child become?
UNACCOMPANIED.
Therefore they go to a detention center because there is no legal guardian available to care for them. Deductive reasoning isn't really your strong point is it...
LOL, ok, you can read between the lines if it makes you feel better.
But this was not done prior to April when Trump started his zero tolerance policy