well, nice argument. i'm not an optometrist but i'll give it my best shot.

big talk doesnt always have a big meaning :

"In other words you can't read out of the corner of your eyes because it is your peripheral vision"
i'll translate what he said into plain english:
he said that if you hard focus on something your brain can't perceive in an accurate manner the meanning of the surroundings (words in our case). because an object which is beyond a certain distance of your eye's focal point loses its clarity and therefore, your brain won't be able to extract any useful meanning of it. so in plain illustration, if i look you straight in the eye i can't look at someone else's eye because the muscles of my eye are arranged in a manner that allow me only to look you in the eye in a clear way at this moment. so if i want to look at someone else's eye i will have to hard focus on that person's eye in order to see it clearly.

obviously this person didn't read the book.
using photofocus i am able to notice and read words which are in my peripheral vision without looking straight or hard focusing directly at them. every one who tried to use photofocus and was relaxed enough in a manner he/she could notice that the words are clear and readable (but the words are in the peripheral vision which is far from the 'noraml hardfocus' focal point which renders his argument useless).

the reviewer said that you can't understand a meanning of a word which you arent hard focusing at. true , i agree that in normal reading fashion it's truly impossible. but when i photoread i am not hardfocusing at it . so i can read, notice and comprehend words which are in my peripheral vision and so is every other human which uses photofocus.

or in eye language:
when using photofocus you don't hardfocus on a particular word. you look beyond the book so the structure and density of your eye changes to a more separated form allowing you to expand the periphery of your focal point and catch the pages of a book in a soft expensive gaze. this soft gaze makes the rods the prime visual receptor. the rods do the job and the cons get out of the way (you don't have to understand the last paragraph it's just an answer in his language).

basically, just think of the eye as a len (which most of it really is). every person that learned optics might understand photofocus better that way. this issue is more plain optics than human biology (optics is a tiny subject in physics), if you know optics i presume you understand that for your eye to percieve something the rays of light must reach your eyes focal point for a figure to be perceived in your brain (just as a rays must cross to create a figure when projected on a len ).
so near and far sighted people are people which their eye's focal point is too near or too far from it's original place so only a part of the rays reach it, causing a blurred figure to be precieved by the brain...just an interesting comment.

sorry if i was carried out a little
hope this solves your question.

Sincerely,
Raanan Hadar