I agree there's nothing wrong with the part quoted. That's an ideal outcome. And the surge of blood sugar concentration from juice wasn't the part I was concerned about (unless it results in a child going into a hyperactive transdimensional shit-fit). The blood sugar crash is the significant part: https://en.wikipedia.org/wiki/Hypoglycemia#Signs_and_symptom...
Low blood sugar also plays a major part in decision fatigue. Do you make dinner after work or buy something on the way home? Making a healthy dinner is the better decision but right now you want satiety. Do you do the washing or sit in front of the TV? You don't just have decision fatigue, you're out of energy - the real deal.
This is in contrast to a low GI meal where the energy supply is provided over a longer period at a stable rate, providing the stamina to make good decisions and act on them.
There's nothing wrong with this except that it probably makes you feel more hungry and eat more. But the blood sugar surge isn't really unhealthy in normal people, it's usually the subsequent behavioral impact (the low that makes you feel hungry) that causes the real harm (ie: the total sugar matters more directly than the glycemic index).