In addition to 60deg left and right, the box upper boundary is 60 deg up. At 150 meters out, 60 deg up works out to be 852ft altitude. At 175 meters out (still in the box) the altitude at 60 deg up is 994ft. Those are both WAY up there, and also still in the box. We all have choices regarding how we want to present the pattern and some (like myself) prefer a large and slower presentation. When I was learning advanced in 2016, I had guys telling me I was breaking the box vertically at the top of the triangle (with snap) and top of the half square full roll up leading into the outside cuban from the top. So I put one of the those altitude sensors in my plane and went out to practice. I was amazed at how consistently the altitude read 805 to 815 ft at the tops of those maneuvers where guys were just sure I was going out of the box. And we have poles set up at my field 150m out, so it's easy to judge and maintain Z distance from the runway.

Now this year in Masters we have the vertical cuban 8, with half roll going up and full roll coming down. Results in a very tall maneuver, again the plane WAY up there as it goes over the top. And again, for overall pattern symmetry and presentation purposes, it's not going to look nice if the other maneuvers in the pattern are small and fast with this hugely tall maneuver stuck in the middle.

Don't get me wrong- Sportsman and Intermediate don't necessarily need to use the whole box, in fact the disadvantage to flying big is that it opens you up to more chances for downgrades. Thankfully the box size allows others to fly big if they prefer, or maybe out of necessity due to maneuver requirements.