...why didn't they use one of those for the Solo? See? Now, you are wondering too.
The likely answers are...
It's Canadian and closer to an Urban vehicle, plus under Canadian rules. There is a reason the Zenn came out of Canada. A lot of parts on that and the Zebra were from China.
So, it maybe they have different supplier types that Elio can't or won't use. For American freeway ready cars I'm not even sure a 2speed control is even available. Golf carts might have that but those parts are directed at lower production levels.
Some of these designs don't scale well and so you don't get much of a price break. It is also likely that at this volume of production the price between a 2speed and variable speed is hardly anything.
For the better control there is also a 'minimum' order. The Mecca isn't at that volume level so they have to take on a different trail of decisions. i.e they may have bought import parts, quality - buyer beware.