Deconstruction the foundation of the calculations, the baseline variables use a 200' ROC, a 50' TCH, ISA temp, and a GPA of 3 degrees.
The GPA line goes though the TCH point, this is the foundation point for the 200' ROC. (so at the TCH, the ROC is 200' below this point)
The ROC tapers from this point, to a 500' ROC at the FAF. (this is what sets the location of the FAF, when the ROC is 500')
This missed approach surface origin is where the ROC intercepts the ASBL which is a projected line level with the RWY.
The intersection of the approach and missed approach used, some using the actual point, while others add a 50' momentary descent.
If you have obstacles, it can raise these surfaces. (blue is high temp correction)
You will not find the "definition" of why it is a 200' or 250' anywhere other than that is what it is. It took deconstruction of the formulas to figure this out.