Wow this is a old post revived :U
True quarter sawn is with the growth rings at right angles to the cut face. That diagram is for how to get only true quarter sawn boards from a log, and so correct.
Yes in accordance with the diagram it is a PITA, and rarely done, but doesn't mean it isn't. I do it for selective highly figured logs for musical instrument grade boards (and other fussy clients) willing to pay to get as many boards as possible from the log. I do it with a bandsaw using an adjustable angular fence. Basically the log is cut to length required, then supported at the appropriate angle by adjustable fences/guides for the quarter sawn pieces. Yes it can waste a lot of timber doing it that way (although I've found uses for the scraps), and takes a long time, but that's where the price comes in (up to $250K/m3).
Keep in mind the Guide is a Novice Milling Guide. I would not expect a high production mill would even contemplate such a methodology. Often quarter sawn timber is mainly offered "near enough" to right angles due to the cost to orientate the log/log pieces. Alternatively a single slice off each face of the quarter is taken for the quarter sawn pieces, then the remainder sold as rift sawn or flat sawn. That is why in the Guide I did show the "other milling" techniques that show the more common quarter sawn/Rift sawn methodology.