the 60mm cutter is good for cutting thicker/heavier fabrics, like layers of flannel; the little dips you get when you cut folded fabric is from your fabric not being folded straight
it may 'seem' straight but if it is not on-grain (the salvage edges are not always straight and should not be used to square up, the salvages should be removed, then square up the fabric using the fold as your straight edge making sure everything is straight and you will not get little v's in your cut edges even if you have 3 or 4 folds.