Judging from the article and abstract (not the study itself), I think it shows that natural reforestation is clearly better than humans doing arbitrary ad hoc reforestation. It does not seem to suggest that natural reforestation would outperform well-designed strategically engineered reforestation. We could make it as diverse as we want.
But it’s interesting nonetheless to be able to conclude that reforestation that is not well thought out is worse than doing nothing. It also means that the greenwashing practice of just planting arbitrary trees to take credit for carbon offsetting is even worse than previously thought.