The issue is the tower is intended to be as high as 480ft. This is significant as that means it will end up being listed on charts and factored into any nearby instrument approach procedures.
All that said, this is a case where the FAA probably shouldn't be dragging their heels. It's trivial (single digit minutes) to figure out what this impacts and shouldn't be more than a day to come to a conclusion and generate a report on necessary approach, chart, and notam updates among others. Unfortunately this isn't how these agencies operate.
EDIT: The FAA reviewed the site multiple times, including earlier this year and found no impact on aviation navigation so unclear what they're potentially upset about. The area is rather sparse and the closest airport is a small untowered field 15 miles away.