That is very much unsubstantiated, all kinds of athletes enjoy and thrive training fasted. It's probably much more complex in what's best for whom than just "much more likely to hit the wall". Type of metabolism, levels of fat adaption, type of activity, length of activity, etc all matters.

As an personal anecdote, I enjoy climbing in the mornings before having food, that's a few good hours of intermittent sprint type activity.