Reading phonetically slows a person’s reading ability down to their speech rate - about 100 to 150 words per min. Speed readers routinely process text at 600 words per min.
BTW, I took a speed reading course in College as a “gimmie” 3 English credits. one of the most practical courses I ever took. Cut my reading load in half.
I was taught to read with phonics. Worked well. As vocabulary advanced, whole word becomes the norm, but being taught to read phonetically works very well, and does not disadvantage you.
I was reading colledge level books in 5th grade.
I took a speed reading course in high school. It was helpful, but of limited use.
I can speed read novels and some magazine and newspaper articles.
It is useless to speed read technical manuals or legalese, where one word can drastically change the entire meaning.
Dense writing has to be studied to be understandable.
I knew one woman with a near photographic memory. She could just page through a book of regulations, and had them all in her head.
But to tell you what they meant, and how they were applied, she had to "bring them up" in her memory, then read them in her head, then consider how they were to be used.
I am not opposed to phonics as it is a necessary skill for when one encounters unfamiliar words. I do believe that phonics should not be the end and as you described, sight reading should be the next “natural” progression to improve reading rate and comprehension.
As for consuming technical material I would say it depends on the technical background. I have found that as I advance in my understanding of networking, topics which I am familiar with can be consumed much faster. I guess it all comes down to one’s habits of reading.
Personal opinion - I believe that phonics can only make someone a marginal speller in English and often works to interfere with proper spelling. My spelling was extremely poor until I learned alternate the alternate pronunciation method.
For example “stomach” I now mentally process as sto-mach not stum-ick for the purpose of spelling the word. “knight” becomes k-night, etc.