The order in which stat block concepts are explained in the Monster Manual is the order in which they are presented in stat blocks.
Took me only 4 years to figure that out!
— Mike Mearls (@mikemearls) February 9, 2018
Welcome to the Monster Manual! @ChrisPerkinsDnD and I organized the introduction that way deliberately.
— Jeremy Crawford (@JeremyECrawford) February 10, 2018