To get back to the main thread. It was indeed changed because there had been incidents where aircraft under RAS had climbed or descended to the level reported. There is nothin wrong with providing a direct readout but, sometimes it is easier to say indicating 500' below. If you are military you are also taught that indicating means unverified and at means it is verfied so no need to add those phrases on the end of the transmission.
Also, setting the QNH is all well and good for terminal issues but if you are providing a radar service across a number of ASRs then 1013 is better.
