It appears to be so

What exactly did it predict anyway?

That isn’t what the article states in any way. A better summary is that an older age at beginning of schooling provides an advantage over starting at younger ages.

No, it did not. The conjunct quincunx at the cusp did it. May you will stay forever young.

https://www.youtube.com/watch?v=Frj2CLGldC4

Astrology “predicts” whatever the gullible choose to accept.

I have twins who were born in August. Not only were they a year younger than everybody else in the class but they were also much more socially immature. This is not at all uncommon with twins who spend every waking moment focusing on each other, and doesn’t give them much experience with social skills in the real world.

When they entered school, I solved that problem by holding them back a year so they would have another year to mature physically, emotionally, and mentally.

The result is they are both fabulously successful in their careers and everything else. It has absolutely nothing to do with astrology.

The point of the article, which mentions to similar remarks made by Malcolm Gladwell, is that the older children do better because they are more mature. Here is an article that describes this belief in more detail, and argues against it.

I seriously doubt it.