That seems like a bit of imaginative thinking and maybe a wishful conclusion. Rather flimsy evidence.
Those forests featured wide open spaces, resembling parks. Today, the same landscape is thick, dense and prone to catastrophic fires that have caused widespread devastation in California in recent years.
That is certainly true here in the Inland Northwest. Forests are choked with weak, small diameter, and short trees. Aggressive thinning is underway in many areas to space the trees out at 20 to 30 feet allowing them to grow a lot taller, thicker, and a lot stronger. That way the fires don't reach into the canopy and consume the entire forest. This has been known for a long time. Good old Smoky Bear really screwed up his native habitat.