Cool IP interesting response perhaps I can explain further. Ground speed is relevant as you point out but you manage those variables and the changes of configuration on intial to final approach where you IAS is changing as you slow by using the simple ROD of rule I outlined above. The reason is that wind shifts with altitude and you can go from a headwind to a tailwind and back again during an approach.

As I mentioned in the above posts you use both the distance readout and altimeter check to verify whether your high (it could be because of a tailwind component) or low (because of a headwind component). This is why it is easier to simply change your ROD and manage your speed accordingly than worry about what the groundspeed is doing all the time the aim is to stay ON PROFILE which is the 3 degree slope. In the real world many approaches have altitude limits which make this very trying but that is what flying is about if you would like to have a go at one that has caused more real life problems than any other try the Localiser approach to RWY 33 at CAIRNS QLD where there are a variety of altitude limits and then what appears to be a big steep dive to get to minimums at the end, using the ROD method makes this not so hard after all.

Once you get used to it is easy to manage and a lot less demanding of brain power than worrying about what the groundspeed is because throughout your approach to final landing your flying the aircraft according to IAS on the airspeed indicator not groundspeed.

It is also a way of managing inertia, reducing fuel burn and letting gravity do the work.

Try it out put your self at F330 on approach to an ILS somewhere with nil wind and do the approach, then do it again with a 30 knot headwind, and then again with a 30 knot tailwind.

You can easily see for example on the ILS that if your indicating 180 knots and your rod is not 800 fpm but say 600 fpm that you have a headwind and vice a versa for a tailwind, managing the ROD will keep you on slope all the way.