It looks like the mining time is for the sake of balance. Because now you can automate wood gathering, and unlike other mods, you don't have to run a greenhouse setup and worry about by-products. I use some mods that let me use wood for other processes (like charcoal or oil), so this mod is still useful as an early game source of automation.
If you look at greenhouses in mods like Krastorio 2, really it's the same thing. You expend water and power, then wait a bit, then you get some automatic wood production.
