For smaller divers that are likely to continue growing there is a way to thread most plates so that it does not ride too low on them. It does put the top of the plate a little higher but it does work. I've done this for two customers who bought set ups for their kids. A year later we rethreaded the plate since, as kids tend to do, they grew several inches.
We also have to remember that these are kids we are setting up for their first BPW most likely for OW dives with no overheads. Is it ideal? No, but at the same time unlike a jacket BC, you won't have to go out and buy them a new one in 6 months or a year. Small plates are nice. Before they were being made though, there were plenty of shorter divers using std plates with no issues at all.
Special sized plates are great. However, like a pair of boots or set of fins, do you really want to drop 150 -200 bucks on plate that may be too small for them in a year? I tell parents to never spend more than 75.00 on a set of fins for kids. 50 is better if they can.
So if a 90.00 aluminum plate will suffice to start out with, it will also serve them a lifetime unless they turn out to be half sasquatch and need an extra large plate. But by that time they should have a job and be buying their own gear.
. I am GUE trained & love diving my system 
