Wow. I am sure the 5BX would make you very fit. BUT, it is very complicated, and requires remembering lots of moves and tables of numbers and timings, and I think many couldn't be bothered with it all.
The very best exercise is the exercise that you will readily and regularly do.
For me, jogging is really really simple, and does not require me to follow any regime - or count any thing. Which releases the brain to think about anything you want. Or nothing. And I never time myself or measure myself, nor run to a beat. I just go at the pace that suits me. That's the ease of it, you just gently plod along. I look around me and listen to the bird song, say hello to the cows, see where that footpath goes etc, And it hardly seems like exercising, it's just jogging along and you get automatic fitness.
BTW, yes, use stairs wherever possible, which is also free and easy exercise
, (I am too impatient to use lifts, which keep stopping to pick other people up !!).