Totally not true. Ambushing an Orc takes minimal resources, so even without getting some land back, killing offensive elites is a big part of Ambush usage and strategy.
This is just another example of poor explanation of in-game features, something that those in charge of wording and communicating these features have somehow failed to improve upon age after age. There's no need to be vague with these things, yet we keep seeing it and players keep having to ask for clarification of a couple features every age. In this case, there are two directly different wordings of the feature in question, but somehow we can't even get an explicit answer as to which definition is the actual function without asking more than once.
It's like talking to a child who constantly dodges the question because they know they're in trouble if they answer directly. ;)