It's not laziness at all. It's the project's Ubiquitous Language, which helps refer to concepts objectively and free from ambiguities. You're complaining because you are not familiar with Kubernetes, and thus you are not the target audience. Do keep in mind you're reading the release notes of a minor release.
With respect I disagree and my objection is that this verbiage is ambiguous and imprecise, the opposite of a ubiquitous domain language. Why does the “declarative API” allow one to “declare or specify”? Which is it? Is there meaning in the clause “or specify”, or is it a superfluous verbal tic? If the API is declarative why is it called a Definition? Declaration and definition are well-used terms of art in our industry but they are not synonymous. And what about “tries to keep them in sync”? Tried by what means? Are they eventually synchronized or not?
After reading your description, "a resource is an endpoint" still seems wrong. Perhaps just lazy, but laziness in technical docs gets confusing fast.