We can argue about the semantics of "wrong" all day, but the lesson here is that not following standards and conventions creates extra work for everyone downstream.
Many responses here seem to be based on the misunderstanding that this is about "not following a standard is sometimes okay-ish", when it's actually about the fact that the standard does not rigorously define what a "resource" is and what it means for the resource to "exist", other than a circular definition based on status codes.
You talk about violating conventions and standards. The conventions are defined by the HTTP spec. The standard is the HTTP spec. Neither are, so far as I can tell, being violated here.