Not sure ! So I will reference my experiences with the system.
Sometimes when I think of a question, I automatically know to search for an answer in a certain place of a book. I'll just pick it up and turn to that page almost involuntarily.
When I come to read the book traditionally my ability to understand the material seems to have increased and I can read it a lot faster. Lots of material is irrelevant in many books and once you are familiar with material u can remember the meaning to whole paragraphs.
I'd say don't expect it to work , just be pleasantly surprised when it does.
It seems to work best on bringing knowledge that you have previously studied to the forefront of your mind.
Why shouldn't it work? You have viewed all the words.
When you use manual activation - pick out keyword and making mindmaps or brainstorming u may find that you get more activations. To be fair though it is hard to pinpoint improvements to photoreading. It works great for projects where you have a very specific purpose.
I am still somewhat sceptical to whether it works completely(esp in the beginning ) but I kept an open mind and it is definitely beneficial in addition to traditional work and reading. It is really a matter of whether you can make it work for you. It encourages you to read for a start , usually I would find difficulty with a subject or it would take too long to read a book and I would give up. I have a very short attention span ( I am not in any way retarded) but it photoreading helps to overcome that to an extent.
So say I should spend 100 hours with an Anatomy Textbook, it is not going to happen so I quite immediately . With photoreading I may spend 10 hours or 30 hours and achieve a level of understanding of the subject that I otherwise would not.