I believe that the implicit claim of this method is that planting a thicket is part of a process, the end point of which is a mature forest, and that the trees which die in the process of thinning from the original density to the final density die with a purpose and their growth and eventual death helps restore the area to a forest much faster than would just leaving it alone.

I do not have the expertise to validate this claim. But I don't think that they're suggesting that in 10 years there will still be 4 trees per square meter, or even one per square meter.