A lot of sold-as pure isomers are also simply racemic. People often won't notice that either (due to placebo and other factors), but they won't be getting the full benefit they wanted.

There are outliers like myself of course that cannot have levoamphetamine, it completely disables me. I do not know why and I don't really care to find out. The one and only time I took regular adderall, I had to sleep it off.