In Australia we only have pure Dex. I'm not sure if I buy that they're a benefit in using 25% levoamphetamine vs the manufacturers just wanted a way to cut their product and get cheaper manufacturing...
The FDA made them remove the meth in the 70s, and in the 90s the company that made it was acquired, and it was rebranded as an ADHD drug.
TBH I do wonder if Desoxyn would actually make a MUCH better ADHD treatment given it lasts in the body close to 2x longer than standard amph.