"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.