There are two things to keep in mind with the Meade focal reducer. Although it's usually called "reducer", it's a reducer AND field flattener. (AND cannot be used with Meade's ACF optics).
For the reducer itself, the changing working distance essentially affects the focal length. So, if you don't match the recommended distance, you either get a faster or slower scope than the f/6.3. The closer you move the camera to the reducer, the slower the optics will be. Therefore, wcoastsands observation is correct that with the closer working distance, he gets a slower scope than f/6.3. The problem with the SCTs is that their focal length isn't constant when you turn the focuser. The calculator is therefore a good approximation. If you want to know the exact f-ratio, you'd better do plate solving.
But back to the flattener part: the working distance is important for the flattener. If you are not at the exact working distance, the flattener will not be able to perform at its best. If you are closer or further away, you will see distortions.
It seems to me that the Meade reducer is also sold under different brands. For these, the working distance (the back focus distance) is given as 85mm.
However, according to Meade's documentation, they have an example, where you'd use Meade's SC-T2-Adapter to connect a DSLR. With the T2-DSLR-Adapters, you usually get a optical distance of 55mm from T2 to sensor (which is/was a standard value for photography) and the SC-T2-Adapter is 50mm long. In total that would be the 105mm that one usually finds as recommended back focus for the reducer/flattener.