The hook scraping he is doing is a German Technique that was popular in the NE USA. I worked with a Pratt and Whitney Journeyman who was taught that method in the 60's at Pratt. He moved to Arizona and was working at Garrett Jet Engines when he and I met in the early 1980's before I started to teach scraping classes at GM. Down at Garrett I was learning how to rebuild Gleason Curvic Coupling Grinding machines. They were then installing a new product called Turcite and a company in MN sold them one and it was going to be rebuilt before Garrett got it.
I have re-scraped to better then new (40+ PPI and .00005"/12" accuracy) a few Moore Jig Bores, Jig Grinders and Moore testing machines. I showed the Garrett Forman my way of scraping, the scoop or push and lift method, he showed me his . Both are used to not leave a burr at the end of the stroke. In My Opinion neither is better then the other.
Professional Instruments who also own Air Bearings Inc in MPLS sent 2 of their Journeymen Scrapers out to Moore to learn how to "Hook" scrape as Air Bearings Inc. back in the 1990's. They were buying from Moore used and new Jig Bore bases to machine a DVD and CD cutting machines. After they learned the Moore Hook technique they hired me to teach them how to use a BIAX Power Scraper to scraper 40 + points. So as you said their are many ways to scrape, none better then the other. The Moore technique is beautiful and for those who want to read about it. Buy a copy of The Foundations of Mechanical Accuracy write by Wayne Moore.
Tom Lipton who Robin scraped his level took one of my Scraping Classes last spring in CA, check out Tom Lipton of Oxtool and get it from his mouth.
I scraped the Moore machines using the technique my Dad was taught by German (1930's) immigrants in MN during WW2 at Northern Ordinance, a huge defense plant. I still prefer to Power Scraper as it is a whole lot easier on the muscles and we can get 40 PPI a whole lot faster then pushing and twisting a hand operated hand scraper. Rich