AutoCad :: Hatch Scale Relate To Any Type Of Distance Variable?

I have been using AutoCAD for many many years and only recetnly discovered the "MEASUREMENT" command. This has allowed me to work out why some hatches are larger than others but I still don't understand hatches! I have a few questions,

Lets establish some things I know,.

1) MEASUREMENT 1 is for us metric people.
2) HPSCALE alters the hatch scale for all drawn hatches after
3) Default for HPSCALE is 1 (tiny in metric)

Now the questions:

1) Does the hatch scale relate to any type of distance variable? e.g. the gap between the lines in ANSI31 is say 5 times the hatch scale or is this totally and unterly random?

2) If there is a logic behind it, does this apply to all hatches in ACADISO.PAT? e.g. scale of 10 produces 10mm gaps in all hatches? (I know it doesn't but there must be some logic to it? Surely?)

2) If the hatch scale is not logical (see Q1) what is the point in the meaurement command and ACAD.PAT and ACADISO.PAT files?