captronk

I am in the market for a touring bike. As I'm shopping around I noticed the Salsa Marakech. It comes in a drop down and a flatbar. Why is the top tube length longer on the flatbar model vs. the drop down? Is it because with the drop down the rider can push down harder on the pedals, the handle bars being lower causing the rider to be more forward and the riders weight over the pedal?

imi

The most often used hand position with drop bars is on the hoods. This is further forward than where your hands would be on flat bars and is compensated for by having a shorter top tube.
This then results in approximately the same "reach".
Longer or shorter stems as well as saddle position (forward/backward) can fine tune reach.

If you make a sketch of this with a "stickman" it will be more intuitive. Even the difference caused by lower or higher handlebars, and the differences with other hand positions (in the drops, tops or with bar ends) can be seen in such a sketch.