It is often thought that every piece of glass has to be ground to enable the foil to stick well to it. There are conflicting views about this. I am firmly on the side of not grinding. The impact adhesive on the back of the foil is thin and will not fill the depressions caused by grinding. It will adhere to a smooth surface more strongly than a rough one. Remember the purpose of the foil is to provide a surface to carry the solder. It keeps the foil in place until the solder bead is completed on both sides. It is not a permanent adhesive. So some of the discussion about which surface is best is academic.
There are ways of obtaining clean cuts that help avoid the need to grind.
Score with an even pressure. This helps the glass break clean with few shells or chips. If there are any overhangs, you can eliminate them with a quick wipe of the edge of the cut piece on the waste piece.
Ensure you hold your cutter vertically. This will encourage the break to be at right angles to the surface giving a clean smooth cut face.
The only NEED for grinding is to adjust an inaccurate cut. We all make inaccurate cuts from time to time.