Guess I misremembered, but there's like 4 different spreadsheets out there for bonus reach on animations that I can find offhand, and most of them give about 10 extra reach on 1hand rightswing over 2hand sideswings. Still brings 1hand swords to within 10 or so reach of greatswords, and that right swing has some crazy range on it, no one can deny that.
I looked all this stuff up a month or two ago and could've sworn I saw an "updated" chart of bonus reach that put 1hand right swing at 40, leftswing at 10, stab at 65, with 2hand sideswings at 20 and stab at 80 but I probably got some numbers crossed.
Regardless you can backpedal a greatsword user doing a sideswing then step in with a right swing and hit them from very far away, very common playstyle with 1hand duelists.