IN A WORD NOTHING.....YOU LEARN QUICKLY WHERE THE FULCRUM POINT IS
Then explain it, based on your experience. I just looked (again) at the installation instructions. Weight pushing down somewhere is going to engage rear brakes. Just as weight applied at some points is going to upshift or downshift (without regard to the ugly shift arm that's added).
From a seated saddle position we have more leverage pushing slightly forward on the rear brake pedal (as we're not lifting ourselves in the process) than pushing down. Separately from whether or not one might accidentally apply rear brakes or shift just by stretching out a bit (which I'd still like more clarification on by the way), since applying brakes is now pushing down rather than forward is there a possibility or even a likelihood of raising oneself up out of the saddle a bit in a panic stop? If so is there a question or concern about raising our personal CG at just he time we'd really not want to do that? Also, in that same panic stop scenario if a rider simply pushed in panic and pushed with both legs might he inadvertently shift while braking?
If the answer to all of these is no and that it's impossible why is it no and how is it not possible?
You chimed in as the expert to defend this product. Voiced by the experience of 39 trips to Daytona Beach. My limited experience can't touch your own. As only an interested viewer of this product I have but you to rely on to effectively explain it. Please do.