For the landings, I think a better technique is to do nothing until the 20 foot call, then chop the power, flare a touch, close your eyes and pray. Works about as good as any other technique.
When asked by a cadet about the height to flare, the standard reply was "point the thing at the crash pint and keep it there. When the captain has a sharp intake of breath and lifts himself out of his seat slightly, then flare - but not too much otherwise the wings trend to get a large dimple the top surface. Works about as good as...........
Regarding RAD ALT call outs below 50'; ask the LOT B767 pilot who greased it on with no undercarriage. I suspect his RAD ALT call outs based on gear height would have been confusing, if there were any at all, which I doubt.