As I understand the procedure construction - a non CDFA approach will have a step-fix to protect you from obstacles intruding into the approach plane so that it is safe to descend immediately to MDA/MDH unless a step fix is there.
Setting the radalt to anything other than ground proximity warnings (100' and 200' for precision and non-precision approach) adds complexity to the process (more calculations required) and is a further distraction if you are slightly tardy in your initiation of the GA - the last thing you want in a high workload situation is the radalt audio bleating.
I find it difficult to understand why the need to initiate GA above your DH/DA is now accepted as best practice for IR - it makes a mockery of the whole idea of Decision height/altitude as you won't fly to your minima - that minima which has been carefully constructed to permit flight to DA/H, then make a decision - then initiate the GA. If you start the GA at 50' above the minima you probably won't get to your actual minima so why have it in the first place.
It rather smacks of something that has been intellectualised rather than kept in its intended simple state.