[altgoogler]

I think the article was pretty well-informed and sourced analysis. Yes, as you point out, NATO has undertaken offensive campaigns. I think the author made a mistake of saying "alliance" here when they meant to say "treaty".

AFAIK, none of the NATO articles were invoked as part of the operation in Yugoslavia. That is to say, though it was a NATO operation, members were not bound by treaty to participate.

This fact muddles some of the points the author made, but the author speaks broadly of the ramifications of invoking Article 5, so I would say their analysis is well-reasoned.