If you are on a sub-orbital trajectory, you have to do something more than “circularize” to get into any sort of orbit. How much more? Well, it depends on what your velocity is at the point where you fire the rocket. If your sub-orbital trajectory just makes it to about the von Kármán line with no more tangential speed than you had at ground level, you only have a fraction (~10%?) of the kinetic energy needed for an orbit. On the other hand, you cannot have anything approaching the minimum orbital speed while still in the atmosphere, as demonstrated by every satellite burning up on re-entry, but any unassisted catapult-launched object must have a higher speed at ground level than it will at altitude. The article’s claim, on a point that is fundamental to the concept, is misleading.