My idea of a worldbuilding guide wouldn't differentiate between new players/DMs and veterans; it would ideally be equally informative to all.
Yes, but a lot of things that are ideal, don't work in practice - especially in writing. Generally speaking, audiences with different levels of familiarity with a topic really call for different presentations.
Consider cookbooks - ideally, the content of a cookbook would be ideally equally informative for all cooks. But, in reality, a new cook lacks a lot of knowledge that an established hobby-cook has, and the professional has yet more techniques at hand.
Which means that a cookbook for a new cook has a lot of information a professional chef doesn't need. And a book targeting a a chef will leave out many things as "understood" that a new chef needs.