In feel like you make it complicated to arrive at your conclusion here. Communism, as described by Marx and Engels and to some degree Lenin, is something very specific that covers most aspects of the society. Political, social and economic. Marx himself wrote books upon books on the economy of a socialist, communist system.
It is not an abstract “I don’t like capitalism so let’s try something different” approach. And yes, many have tried to adapt it, as you mentioned which is why those different approaches carry a different name ‘anarchist communism’ in your example. Because they are different enough from flat out communism.
Without search engine and without going into detail that is out of the scope, anarchy is a different path to a classless system. Said classless system is different enough from communism to warrant discussion but close enough for that discussion to be devolving into anarchy vs socialism most of the time to differentiate the path to that system.
Said path in anarchy is comprised of setting up collectives that start small, neighborhood small, and gradually evolve. Each collective shares almost everything between its members and there’s no leadership or ranking across its members.
Anything deeper than that leads to a long discussion that is out of the scope of this thread and definitely out of the scope of the ELI5 the post I originally replied to needed or had the philosophical basis to understand possibly. I’m not saying one is better than the other, but they are quite different approaches to a similar goal, a classless society that money does not rule all.