The Wiki shows a distinction between the scything and guillotine strokes. In reality there is little difference though, to my mind, the guillotine stroke more accurately depicts how a scythe actually cuts.
I don't consider the scything stroke to actually involve a pivot. Yes, using an actual scythe does involve a circular motion but the contact between the blade and the individual hay/straw stem is not circular. The blade is slicing the stem. To see an actual scythe in action watch this.