It won't cut everything, though! It cuts a 15x15 square of grass (See Here), so that's 7 squares to either side of where you're standing, and 7 squares up and down. It absolutely won't clear your entire field for you with one strike of the fully-charged mythic sickle from your farmhouse.
Alright, I understand a bit better. I had watched a youtube demonstration and I was like, "wth, it'll destroy everything!" It's not gonna be that useful. But it'll be worth it for completion, end game stuff.