The parent poster isn't inventing anything or deciding anything. They're just sharing what the common understandings are.
Stating something authoritatively is, in fact, "deciding" it for others.
> They're just sharing what the common understandings are.
No, it is not at all the common understanding. When I put "anarchy" into a search engine, the first thing I see is "Absence of any form of political authority.", because that is the common understanding. Forming an "-ism" around that is commonly understood to follow the usual patterns.
Perhaps people who apply the label to themselves wish to see things that way, but they are (thankfully) a small minority of people.
I don't give a damn about the justification, because there's clearly no good reason to care, as it clearly serves a dishonest and dangerous political purpose, viz: attempting to delegitimize the state in order to seize power.