TBH, I think it is sales speak rather than of any technical value.
You can't simply take 23% THD and say that it has any meaningful relationship to power. But that's what the author has done. The 23% THD in current adds 23% to the total power? That's just nonsense. Apart from anything else, harmonic currents are at multiples of fundamental supply frequency. You can't treat them in the same way.
Take a simple example. Imagine your THD has just a second harmonic component and that it's zero crossover is at the same time as the fundamental. In the first half cycle of the fundamental, the second harmonic will have made a full cycle - half positive and half negative while the fundamental voltage is all positive. The power at the harmonic frequency is net zero.
I also have a bit of a problem with the contention that a magnetic ballast takes non-linear current. And quite a lot of it. Maybe the wound components operate into the saturation mode. I don't know.
And this statement:
"However, solid-state electronic devices have been shown to be the
largest contributor to distortion due to the switching of diode bridges producing a discontinuous current, which then causes a distorted sine wave."
from someone promoting electronic ballasts seems like a bit of an own goal.