shagrat, I've been thinking about the ALR-67A(V) again recently and your specific question. I wonder if the changes were made, simply due to a change in the primary threat display type. Initially, the primary display for the ALR-67A(V), was the IP-1276/ALR-67 azimuth indicator and at around 3 inches or so in diameter, the display is rather small. Having critical threats (the most important) within the innermost ring, particularly in a high threat, multi-emitter environment, could make the indicator difficult to read, as well as making it more difficult for the crew to determine the azimuth position of the threats, thus the critical ring was placed furthest from the centre.
Later on, aircraft such as the AV-8B introduced the MFDs/MPCDs as the primary RWR display. The vastly increased display area over the IP-1276, afforded threat symbols the benefit of much more room and radial separation, mitigating a lot of the overlap that may have occurred with the older display. Because of this, the software engineers probably decided to go back to a common sense approach, of having the critical ring threats closest to the inside and the non-lethal threats on the outermost ring.