One of the things talked about in a lot of speed reading circles is subvocalization, and not doing it. I assume if you're taking in several lines at a time you're not reading to yourself in your head and just seeing the words and understand them. I've tried this, but find it difficult and feel like my comprehension goes down. It also takes a lot of effort to actively change how my brain handles processing text, so I get tired of it rather quickly.
My mom read to me a lot when I was really little, pointing at the words as she read them, and as she tells it, one day when I was 3 I just told her it was my turn and I read books to her. She figured maybe I'd memorized a couple favorites, but on our next trip to the library, she found out some switch had flipped in my head and I was now "a reader."
Neither of my parents had younger siblings or cousins around and I was their first, and apparently they didn't remember their own childhood reading learning very well, so, "Oh, I guess she reads now," was as far as they looked into it until my preschool teachers were very surprised when I started the next year.
I don't really have any explanation for it other than "when I see words, I know what they mean," so unfortunately I don't think it's particularly helpful or generalizable. Just a quirk I guess.
When I was young, I thought it was so strange that they would slow people down like this. It wasn't until I was much older that I realized the way my brain flipped the "on" switch for reading was different from how most people read.