Cause she's essentially trying to improve an Archimedes' and Eulers' method/work by making a simple conversion - which for some reason she superficially laments a conversion, but then goes ahead and uses one in a more confusing (and less intuitive) manner.
I think her attempt is to explain to the lay-person why it's "better" or "easier" for one to use π radians instead 2π radians for the measurement of circumference.
Essentially, her conversion simply applies a factor of 1/2.
However, if you were to study Descartes and Pythagoreas and the unit circle, and how Archimedes derived π... As well as the various calculations used in applied trigonometry (which essentially revolves around angles and the unit circle)... It's much more intuitive and sensible (and easier) to use 2π for the radian measurement of a circumference when it comes to calculations.
Like I said, her method is correct, but I don't understand why she's trying to improve on Archimedes and Euler and the great mathematicians throughout history, and the beautifully elegant, commonsense, and accepted methodologies they derived and which have been used for millennia.
In my opinion and from my perspective, she means to make things more understandable but is just making things more confusing...
If you'd like to understand more, I'd suggest you study the unit circle, sin/cos/tan, Archimedes and the geometry of a circle, Cartesian coordinates, Euclidean geometry, etc.
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