I'm not sure what else I can write to convince you -- I've detailed how I "read" so quickly in a few comments on this topic. It's true but I don't think it's all that unusual (your comment is making me think it may be which I'll try to keep from going to my head).
I used to work in Infrastructure in the early 2000s and a coworker and I had a running contest on how many certifications we could amass (my company had a library of reading materials). It was my coworker who pushed me to take a speed reading course. We'd each read 600+ page books covering the material around 3 times (maybe 4, but later reads are not complete reads) over a week while testing each other at work. Both of our pass rates were perfect[1] (Novell CNE, CNA, MCNE, A+, Security+ -- do those still exist? -- and a myriad of other certifications of dubious worth) -- failing meant we had to pay out of pocket, so we passed.
The "first read" is a skim/scan, very superficial read, and it's easy to get through a large book this way, especially if it's material I'm already comfortable with. The 1000 page books are technical books (points I made elsewhere) that aren't all wall to wall content, lots of diagrams, code, etc. I read a book more than once if I want to learn the content (the first read is partly to weed out a book that has no value to me).
At the end of the day, it's the equivalent time it takes to learn the material that matters. After a 2 hour "read" (skim/scan/speed-read) of a 1,000 page book, I'm nowhere near where I'd be if I had read the entire thing, slowly, word-for-word while taking notes and doing exercises. If I feel the book is worth it, I'll read it again, then read parts of it carefully, to the point where I've likely read the book 3-4 times with notes and exercises included. I'm at "equivalent to reading it slowly" by the end of the second read. But that's a low bar for a book of that size. Considering that same exercise would have taken me a month to complete the first read. How much of Chapter 4-6 will I remember on day 30 of multi-evening broken-up reading sessions reading it "slowly"? How likely am I to be burned out by then? By doing it this way, much more of it is fresh in my mind and (most important to me), I'm more likely to devote the time to learning the material knowing it will take a week, not a month+, to get what I want out of the book. After finishing a C++ book recently, I was writing in the language. I'm nowhere near proficient, having only two books and a 10-year gap in my C++ code experience, but "the old way" I would have been more likely to let it sit on the shelf half-read, never completing it. If I did, I wouldn't have been able to write more than a "Hello, World" program without having it pulled up along-side my IDE, constantly referring to bits I hadn't read in over a week.
[1] Pass rates, not scores. There were some tests I squeaked by one question over passing. I scored perfectly on more than a few, though, too.