The intent of equality is to give people the same or similar opportunities and outcomes, whether that be in social matters, or based off necessities. So in terms of the child not being tall enough to see over the fence with equality would be giving the child the same opportunity to watch the game as the others by giving him another box to stand on. The part that was equal about it was giving everyone the ability to watch the game, and not the giving of the same tools to each person. If someone didn't need the box to comfortably watch the game, why would they need it?
Just like if you were to feed 2 different people with different weight and size and age. A 180 pound man will not eat the same as an 80 pound child. The equality term would be they both get the same equal opportunity to not feel hungry by giving them the calories needed to sustain.
Some people would explain this as equity, which has multiple debates already between equity and equality. But the definition of equality includes the term opportunity so I stand by the concept of equality as long as it is understood and explained correctly.
Here are some articles that go more into detail on the equality vs equity vs justice if you were interested: