Flutamide is a weak anti-androgen. 

http://www.cancerbacup.org.uk/info/flutamide.htm

It hasn’t really been tested that extensively in children.  Normal children’s androgen levels are a lot lower than adults androgen levels.  So althought it may be ok to use in adults, one has to wonder if even though it is a weak androgen, if given at too high a dose, I suppose it can suppress androgen completely in kids.

http://www.cancerbacup.org.uk/info/flutamide.htm

Children are meant to have androgens---just in lower amounts that occur in CAH.  otallt blocking or lowering them substantially in the presence of continuous high cortisol levels well high when compared to the androgen levels which have been suppressed or lowered) would be just as likely to cause weight gain and insulin resistance to my mind.  When we over treat a child with cortisol we do exactly the same thing.  We suppress androgens too much and that is why growth is suppressed.  Children on conventional treatment are exposed to androgens where the cortisol falls low enough in their blood serum to effect release of androgens.  So they get a good dollop every few hours.  Children on those drugs are going to get less androgen because flutamide may do all the things that is stated in that study but it is an anti-androgen and could be suppressing it too much.  They are either using too high a dose of flutamide, too high a dose of cortisol for the levels of androgens present after flutamide has been given OR, flutamide is not good for children full stop because of there being more difficulty controlling children on it than just conventional treatment. 

Doctor’s cannot make up the minds what exactly the correct "normal" levels are where androgens are concerned (and I believe these alter with age of the child so it isn’t as simple as aiming for between 500-1000 ng/dl obviously) in conventional treatment, then there is even a scarce or smaller chances that they will get this treatment right IMO.  That’s because at the very least kids on convetional treatment get a good rise and fall in androgens and cortisol.  kids on this treamtnet are being maintained at the same level of androgen and same level of cortisol over a 24 hour period, and they are not able to recover from either via negative feedback mechanism.  It’s like being in limbo basically.