Well, I don't see any specific "advertisement" of child fares on the specific route in question on the .com website.

The text you found says that children under 12 "travel for 75 per cent of the regular price of the flight on most routes and on almost all fares"; even if you discount that any US-Europe route cannot offer a child fare, the text is not incorrect.

If you were to search for Atlanta to Cape Town tickets, for example, you will see that US-originating passengers are eligible for a child fare; so it's not that there's a blanket ban on child fares for all US-originating passengers; even when departing from the US, you can still have a child fare on some routes...