I've been doing it this way for a few months now and kind of just drifted toward it as I refined my technique of muscle focus. It wasn't some laid out program I found in one place. It also didn't just pop into my head, I study this stuff a lot and it's been a natural progression as I learn more and more.
Having said all of this, I just read a post by a personal trainer that spells out what is going on in this type of workout infinitely better than I ever could. The trainer's name is Drew Baye and his post is here. I highly recommend you read it, even if you don't plan on changing things (it's required reading for you Mom).
I personally only do one or two reps with six different exercises, split between two workouts during the week. As you will see in Drew's article, the number of reps, weight, and time under load are not the goals, they are a means to an end. As he perfectly sums up:
Don’t think of exercise as using your muscles to do something to the weights – think of it as using the weights to do something to your muscles
Mama Aspen Paleo lifts superslow BBS style once a week at her local fitness center and I couldn't be more proud. It's not her fave, but for such a small investment of time she knows the benefits are well worth it. Rock on Mom!