I may be able to shed some light.
Taking Canberra for example, on a typical cold winter morning of -5C, the altimeter over reads by about 100' at the outer marker, but only 20' at the minima. If the temperature was -15C, the error at the outer marker would be about 150' and, at the minima, 25'.
On a typical Canberra morning, if you were to follow the old AIP procedure, you would unnecessarily add 100' to the minima.
The new procedure, IMHO, is a gross error check that guards against such things as false glideslope captures, having the incorrect chart or having the incorrect QNH set (eg. 10 mb/300' error). I don't believe it was ever intended to have the OM check height as a tool for fine tuning the minima.
For more information about altimeter errors at cold temperatures, look
here.