I am not familiar with the source you are refering to. But I was taught what was called "Image Streaming" by Paul Sheely at www.learningstrategies.com in his Photoreading program. This teaches you to process information at 25,000 words a minute.
It is not speed reading. It uses whole brain learning methods. It works.
The image streaming he taught was to relax and recall a past vivid experience to another person or a tape recorder. Recall everything about the experience, access all the memory of all of your senses, relive the experience as much as you can, and SAY IT ALL out loud. This makes the brain hemisphere link work harder, which increases memory ability and is supposed to increase IQ by .8 points per 20 minutes of practice. He quoted some study on this, but I do not recall it. I am sure he would answer the question if you asked.
I believe this technique this is covered in his book on photoreading. You can buy it at the web site listed above. The key is getting the right brain total database of past experiences practicaly linked out through your verbal logical left brain into words.
I would believe there is a point of diminishing return. Most of us are not use our brains efficiently, but who knows. How do you rate the IQ of people who can do very complicated math in their heads, etc etc?
Lacking a really good definition of what intelligence even is, knowing the limits is hard. Some of the things people have done with Photoreading, things I have done in my work, defy logical explanation. Any time you can really tap the right brain, the left brain can not really grasp it. IQ specs is a very left brain concept. True intelligence is so much more than what those tests can quantify.