For positioning I can see that, but I was asking about the importance of knowing whether the spectro centre-weights the measurements - which I wonder whether an i1Pro 2 does. It knows where it is by virtue of the striped grid it is reading as it moves along and the patch it is reading in real time; its reading is timed as so many samples per second; to centre-weight the samples in time it would have to do complex calculations with instant feedback tracking the varying speed that the user deploys reading a row. Seems improbable. The iSis is a different animal - fixed and known speed so fewer variables in real time.
Yes, the iSis does have those advantages. The I1Pro2 would have to window it's samples, excluding those where the 4mm aperture has potential for overlapping two patches plus accounting for error. A design approach would be quite straightforward. Include all samples in the window, add them, then divide by the number of samples in that window. It may, or may not, include some sort of window rolloff like the iSis which uses a Gaussian window giving the most weight to readings within 1mm of the patch center. I would think that part of the program code could be quite similar. The only reason I can think of for not using a rectangular window is that if registration errors occurred or the paper dried with a slightly uneven shrinkage then a Gaussian window would reduce those errors.
But there is a tradeoff. The Gaussian window images a narrower part of the patch and so paper irregularities are more likely to show up. It also increases the noise (less photons) but that effect is miniscule. The illuminant is so intense that the shot noise is vanishingly small when measuring reflectance spectra.