The difficulty I have is with the idea that equidistance is more important than topography in placing a particular monument somewhere.

Because for me, most BA and Neolithic monuments appear to be placed because of where they "ought" to be, not how far or otherwise that is from any other monuments in proximity. For every group where the measurements (on a map, not on site) suggest distance is important, there must be 100 more groups where the measurements do not.

At Maen Llia, the placement of the Rhyd Uchaf cairn seems to me to be based more on the fact that it's on a prominent little hillock in the landscape, between branches of the watercourse, looking down the valley, than how far it is (on a map) from Maen Llia. 10 yards either way and it would be in a stream, so the position is dictated by the terrain not the distance from something else. And the cairns on Fan Nedd are surely placed in the most suitable location based on the underlying topography, not how far they are from each other.

I'm not discounting the possibility that a particular monument may be deliberately placed x metres from another monument, but surely that can't apply to the vast majority of monuments that we see in the Welsh uplands? There seem to be far too many other factors involved that would override equidistance, aren't there? Not least of which is pure practicality in a very uneven landscape criss-crossed by streams.