I would have loved this method, my kids would not thrive with it.
I loved CLEP exams and stuff where you just study, take the test, and demonstrate mastery. I wish schools did this more, but I think they want to keep you there.
I had a year where I was really independently studying where I would check in each day to show off homework and tests and then just run around outside for the rest of the day. I would have about 15 minutes of “school” each day and then just play. Or I would do the whole month or semester in a day and then run around.
It’s hard to know how effective it is. I had fun. And I still remember fractions and George Washington and stuff covered that year. And I did well in “regular” school after that.
It’s just a big risk to run with kids so I don’t think schools want to do it at scale.