Class E PA is better than other class PAs?

Here is a paragraph I read in a book talking about how Class E RF power amplifier has more benefits than Class F, Class B and other classes PA regarding low voltage operation. But I can not understand it and can't figure out why the effect mentioned in this paragraph is less pronounced in Class E PA than others. Here is the paragraph.

"As the power supply voltage decreases, the value of the optimum load required to achieve a specific value for output power also decreases. This decrease in the load resistance will increase the matching network transformation ratio from 50 Ohm, causing more losses in the matching network. This effect is less pronounced in class E than classes B, C, and F, making it more suitable for low voltage operation."