On its own, you're not going to magically be able to reduce your reading time by 95% and still maintain the level of retention you get by a slow word-for-word read from a few weeks with an app/course. As the article states, there's more to reading than just swallowing a word more quickly. But the techniques enable you to change the way you consume information by eliminating the bottleneck and associated procrastination of staring down a 1000+ page book and the weeks it will take to get through it.
I'm a huge advocate of speed reading, personally[1]. However, I think the points made in the article have a lot of merit.
Speed reading should be seen as a tool for consuming information, but you have to adjust the way you learn accordingly[2]. I can read, cover to cover, a 1000 page book in a few hours. My strategy for learning from a large book is to read it more than once (often three to four times) to treat the first read as a 30,000 ft view. I don't do included exercises, and I also limit my note-taking. My second read is with pen and paper in hand. I break for exercises and notes, but otherwise continue to read just as rapidly. If I struggled with the concepts, I'll repeat the process.
Years ago, that book would have taken several sessions to complete the first read and the second read would only be over particular sections. I'd be done after weeks, rather than a weekend, which also negatively affected my retention. Reading from day 1 is built upon and by day 19, it's foggy. When I can do that in an afternoon, it's fresh on my mind. And at worst, with several reads, I'm still getting through the material in half the time it would have previously taken me and with solid retention[3].
It's also not something you become good at over night. After I took the course, I could read twice as fast, but not twice as effectively. It requires a lot of practice. When I sit down to read something, I have a goal of learning whatever it is I'm trying to learn, but I have a second goal of consuming that material more effectively. The first few years, I focused on reducing my time spent on the first read. As the years have gone by, I've adjusted my note-taking and methods for retention. I read a 500+ page book (often equivalent text in PDF) nearly every weekend. I pick things I am using today and grab books that build on that.
[1] I took a multi-week course that focused on the typical "eye movement" techniques along with skim/scan techniques. That course started, for me personally, a rapid change in my ability to consume information from text and I still believe it was one of the most important classes I've ever taken. I greatly prefer book reading over courses these days because I can completely control my pace from very rapid to word-for-word.
[2] I'm speaking purely of technical reading. I do not speed read fiction and my personal experience is that speed-reading fiction is awful. I stick with audio books for that.
[3] I do not have data to back this up. I've been reading large, technical programming books for 18 years, and some of that added speed is that I have a relative understanding of the work before I begin. I know how to read a programming book to maximize my retention and I read programming text to become better at what I do, which is something I've learned how to do from years of practice.
[Edit: Added a note clarifying fiction vs technical]