Why Uniformity of subpixel in image analysis ensures correctness
If the subpixels are not roughly evenly distributed then this means (among others) that certain decimal values are more prevalent than others and this can lead to large gaps in tracking the particle (gaps which can be larger than the particle's size).
So this amounts to saying that the outcome is not very precise.
On the other hand, basic continuity of motion requires that decimal values should be evenly distributed on average.
For example imagine the subpixels have a prevalence of 0.1 and 0.9 decimal values. So for a particle of size 1 its positions may vary by more than 2 pixels (eg 1.1-2.9) so this creates inaccurate trackings on average.