It's true, but also takes way too long for the mission at hand. Trees already grow slowly, and squirrels/birds were going to eat a lot of the seeds which -- as

It's true, but also takes way too long for the mission at hand. Trees already grow slowly, and squirrels/birds were going to eat a lot of the seeds which -- as we can see here -- is counter to incentive when there is a dearth of seed. This is not even to mention the ungulates, which will eat most of the young trees. Simply put, a managed plantation will produce better outcomes than "hands-off" rewilding or even a hybrid model. It is better still if the wildlife are managed or contained. Healthy forests have predators to provide pressure on herbivore populations; predators were often intentionally removed in many of the places we are now considering for afforestation. But that said, theoretically: yes, absolutely, a tree planted as a seed by a squirrel, if it survived to old-age, will likely have grown faster and healthier than the equivalent nursery product tree, which would have endured lots of handling and some shocks at a young age. If I were to guess at the type of innovation we might see in this space, I would say GMO trees that grow at enhanced speed is more in the vein of what might be deployed. If land were more readily available, like in boreal regions, then you might see some sort of innovation in the form of novel rewilding techniques, like you are suggesting.