That "visualization part" is unfortunately, for the majority of people, how the human brain creates meaningful neural pathways and absorbs information. Not necessarily in a "visual" as in involving images way, but some form of connection to something you already know whether explicitly visual or abstract is how the brain creates memories. In my experience speed reading, it dramatically increased the rate of information intake, especially if using software to sequentially display text (like Spritz), and eventually with practice it was possible to retain comprehension as well, but never was I able to create lasting stores of that information. I could get through a non technical book in a few hours reading consistently around 700 wpm (taking breaks to rest the eyes) and could understand what I was reading in the moment, but can't say I remember much of anything from those books. They literally feel like a "blur" in my mind.

Perhaps if the goal of reading is to identify specific information anywhere within a text quickly and move on to something else or switch to reading more mindfully at that point, then it may make sense. Personally, I read exclusively to obtain information and retain it. If I don't care to retain the information, I won't read it in the first place. So not being able to retain anything meaningful save for the few instances I slowed down ended up defeating the purpose for me. Lastly IIRC, I once read about the neuroscience of reading with regards to speed reading and the gist of the article ended up saying that it takes discrete periods literally measurable in observable time in order to form memories, and speed reading feeds in information continuously at a rate that does not allow for this crystallization to occur--because the actual reading is like a blocking operation neurologically to memory formation. When we read normally, we pause and reflect in various abstract ways on the information which creates connections and hence memories.