Between decades ago and now we've recognized that sugar only causes excitableness in children who are prompted (Clever Hans style) by adults who expect such an outcome.
The wisdom you're referencing is circa the 70's, it's been attempted many times since and has never replicated.
The comment you're replying to doesn't seem to mention the debunked "sugar rush". The "crash" on the other hand seems to be more replicable.
Also your framing ignores that the "prompting" can be circumstantial rather than targeted. The "rush" is frequently misattributed to sugar when it can actually be better explained by the food itself being a rare treat (and thus exciting) or the situation in which it is provided being special (e.g. a party). Or it can simply be the joy of eating something very tasty.
It's less Clever Hans and more "kids are more prone to sudden outbursts of strong emotions and adults blame it on food".
The wisdom you're referencing is circa the 70's, it's been attempted many times since and has never replicated.