That looks like differences due to the analysis blocksize - it's mainly affecting blocks with little detail, which can be matched quite freely. More freely when the blocksize is small. You should compare the vectors before and after they were scaled - that's what the plugin does and so those clips should be equivalent. The plugin cannot guarantee that a search with a larger image/blocksize will be identical to a search with a smaller image/blocksize - that's down to the operation of MVTools. Although in practice those searches are similar enough for some purposes. Vector scaling will be used for faster QTGMC presets on HD material.
Change the last line in your script to show original vectors, then small image vectors, then scaled vectors:
Code:
interleave(MShow(supersc,fvecnormal), MShow(superScaled,fVecScaled).Spline36Resize(clip.Width(), clip.Height()), MShow(supersc,fvec))