I just googled EAS. So are you referring to the sports nutrition product, Energy Action Scotland, Employment Agency Standards, the European Athletes Society, European Astronomical Society, or are you just throwing in an acronym for the sake of it?
The graph in the book is a simple demonstration of relative turning circles. It's not scientific. It's very 'layperson', but not necessarily 'wrong' per se.
I'd say the altitude is a typo. The x and y axes obviously show the same parameter, i.e. radius of turning circle in feet. But I have the book, so I'll check if it's clarified in the text.