Some kids like workbooks or curriculums or even going to school. To me unschooling means allowing your child to use the materials and learning methods that they want to use. So, if your friend is using that curriculum because her child likes it, she can still be unschooling.
I believe in strewing. I buy many of the secular books off the www.sonlight.com booklist. I don't get the instructor's guides. I share the books with my kids. Those they enjoy are read over and over. Others just sit on the shelf. Maybe they'll be read someday, maybe they won't. Just like the other books I buy.
My kids are still young, 2.5 and 5. We let our 5 year old have screen time while his sister naps. We have a collection of children's documentaries or he can watch youtube. He has totally free access to www.starfall.com and a couple other phonics sites. I don't want him spending a lot of time on the computer at this age. However, around 6 or 7 we may get www.time4learning.com. He will have free access to that. One friend has it and there are days her daughter will play with it for 8 straight hours then she may go days or weeks without using it. That is how we will use a curriculum.
We'll see what happens as the kids get older. We are so far away from then that I'm not worried about it. I don't know who my kids will be or what their interests will be. There was a time when I wanted my kids to have a rigorous classical education. Then it occurred to me, "What if they're not interested?" If they want to go to college, they will do what they need to in order to get into college.
I had a reasonable public education. I remember very little of what I learned. And what I learned was fairly arbitrary. I remember learning about weather in 8th grade and I remember very little of what we learned. Really, for me to understand anything about weather I need to look at the internet. We have a preschool book about weather and talk about it from time to time. My guess is the subject will come up again when they are 8th grade age. When they are adults if weather is important to them they will learn about it. If it's not, they won't.
About the only thing I figure kids HAVE to learn is reading, writing, and basic math. Beyond that, they will learn more about what they are interested in than they could ever learn in school and the rest of it just won't be that necessary to them. If it's necessary, they'll learn it on their own.