I think John Taylor Gatto pointed out that some children learn to read when they're 2, some when they're 8, and by the time they're 12 you can't tell the difference.
I met a man who was traumatized when his first grade teacher tried to force him to read, before he was ready. The lesson was put in front of him, and 1st-grade-him thought he was stupid for not being able to perform.
"illiterate for years" is of no consequence when we are talking about 5-8 year old children. The point was there was no discernible difference in children who learned to read a a variety of ages.
In factory schools, if one is "delayed", that classification/label is attached to the child and becomes a part of their identity. Few escape it. Similarly, one who reads well at age three is held up as "gifted", and placed on a social/academic pedestal.
People have a wide variance of ability and timing during normal development. saying "it's much less stressful to learn to read early" is arrogant and naive. It's extraordinarily stressful to a child to be told they are stupid/slow when they are simply not ready, and stereotyped and classified as a result.
Gatto's quip aside, there are actual studies that look at correlations. "Using third-grade national percentile rankings... into below (0-24th national percentile), at (25th-74th national percentile) and above grade level (75th-100th national percentile) groupings, we find correlational evidence that students who were at and above grade level in third grade graduate and attend college at higher rates than their peers who were below grade level in third grade." https://www.chapinhall.org/sites/default/files/Reading_on_Gr...
https://www.gov.uk/government/publications/reading-and-maths... found a 10% difference in earnings at age 30 for differences in reading skill at age 10.
"Phonics" is mentioned a few times in the interview, ie, the connection between (English) spelling of written words and the spoken language they represent. I immediately found myself wondering how this relates to how children learn to read in other languages whose written forms are either far more phoenetically entwined with their spoken forms (eg, Portugese and Finnish, as I understand it), or far less (eg, Mandarin or Arabic). (I'm sure I'm oversimplifying complex relationships and reality in the overbroad sentence I just wrote, but I'm happy to hear how my received CW is wrong about these languages.)
Anecdatally: when my own daughter was about four, we had some friends whose son had learned to read from a Phonics book at four, and when we knew him at five, he could read pretty much anything you put in front of him (how much he understood, who knows, but he could translate the text into spoken language that we could understand). Both her mother and I were also reading at four, and so we expected our daughter would be able to do the same. We were inspired by this kid's example to get our daughter started early, and tried the same Phonics book with her.
Unfortunately, she didn't take to it so well. She seemed to understand what was happening well enough, but it never clicked or became natural, and it was ultimately a frustrating experience for us and our daughter. So we eventually stopped the lessons, and let her learn at her own pace. She happily made it through kindergarten and first grade without really showing any interest in or being able to read with any proficiency. She was clearly smart, and her teachers told us not to worry about it. Then in second grade mid-year, something just clicked, and she started voraciously consuming books, with her reading ability testing well above grade level.
Now at 16, she's still a voracious reader, and a writer who has completed NaNoWriMo three times, reads and writes every second of the day, and has an incredibly sophisticated grasp on storytelling, analyzing the writing behind books and movies and TV shows with a clarity that I personally have never had.
So, how did she learn to read? I have no idea. It wasn't phonics. But I suspect she would have managed it no matter what instruction she received. I also doubt that she is really a meaningful example, other than to say that it's complicated, and humans vary in their learning styles, and we should focus on the goal of reading and comprehending, trying to discover all the ways that individuals can and do learn to read, and having our teachers focus on identifying and encouraging the best methods for each student and not so much on imposing specific mechanics of how the statistically typical student achieves reading proficiency.