If they measured only weight loss, then yes, it's due to the reduction. But it's important to note that the reduction wasn't forced on them -- it arose "naturally", meaning intermittent might be an efficient strategy to lose weight (e.g. the person wouldn't have the burden of tracking calories).

That's regarding weight loss alone. Various health and cognitive benefits are usually talked about in the context of intermittent fasting, and that seems to arise from being fasted rather than from being in a deficit.