I'm not sure about design either. The speed is variable though, so if you were getting it to mix chemicals, you would just use a lower speed. For a yeast starter, you essentially want to get it going as fast as you can without throwing the bar. They also use the exact same teflon coated stir bars. I think the idea behind them is more economical than anything specifically designed for making a yeast starter. Afterall, there are plenty of homebrewers out there using lab stir plates too.
Just thought this might be a good option as they are always available, and you don't have to hunt one down on Evilbay.