I am fairly confident that the article is not trying to imply that Chrome/Safari are NOT standards compliant. The author seems to be trying to heavily emphasize

I am fairly confident that the article is not trying to imply that Chrome/Safari are NOT standards compliant. The author seems to be trying to heavily emphasize that this is not a Firefox bug, and that Firefox can legitimately do this while being standards compliant. I feel like the author was anticipating a lot of people blaming Firefox for this incident, and is attempting to shut those responses before they get made. I think that trying to write to the responses you expect from your audience unfortunately ends up with these kinds of miscommunications of intention more often than not.