The fretboard end not moving(in other words relief is set and can't be corrected), is exactly why it IMO should be included in any relief measurement. It's the reference point to determine whether a neck has a simple bow, hump or possibly both, which would be a serious problem. Also action is set in correlation with the relief of the entire fretboard. The fretboard does not end at the 15th fret. Imagining it does is the wrong kind of pragmatism.