Even among Theravada Buddhist meditation instructors there are clear disagreements on what the experience should be, how concentrated the mind should be, etc.
For example, for something as simple as a pull-up there are questions like: what muscles are being worked? What is the proper form? Pronated or supinated grip? What pace and why?
If I read an article on any subject I expect to see lots of footnotes.
Meditation is something way more subtle than doing pull-ups, yet most guides seem to assume that there is one concrete definition in the learner's mind. Where did the prescribed method come from? What is the goal? To just put instructions or information about any subject without mentioning background or citing any sources is strange to me - is meditation so new, obscure, or insignificant a subject that it doesn't warrant a little more rigor?
TLDR: meditation is a bigger subject than most people reslize.