I had 120 logs taken off my property last June/July. They cut anything 18" or larger. I didn't let them cut several large white oaks, red oaks, stand trees, and they didn't want pin oaks. My goal was to open the canopy to allow more sunlight to my white oaks and the forest floor in general. I made them drag the tops into the woods and not leave any in my field or on any of my main paths or roads. It was ugly as heck last fall and I questioned what in the world I did. Looked like a tornado hit my property. One year later, undergrowth is 4-5 foot tall and you can't tell the cutting happened other than a few large brush piles. There is MUCH MUCH more browse for deer and wildlife to eat now. It hasn't seemed to alter the deer travel routes much. I've never seen this many turkeys on my property either. So I'm pleased with it.
So Bushman if it is done right the first year your hunting will be off but it should improve in future. To be clear though I'm talking select cut and not clear cut. If I was your BIL I'd make sure they were in and out before the fall rains start though. Harvesting timber on wet ground tears the heck out of a property.