One could argue that software architecture is the inner structure of an application, i.e. the libraries, modules, classes, functions and, most importantly, their interfaces. The GOF design patterns are purely a matter of software architecture, for example.

System architecture on the other hand describes the different applications/services that compromise a system, including the ones that you write yourself, plus the ones that you just "use", e.g. database, storage, load balancer, etc.

I would argue that the article mostly talks about system architecture with focus on storage and I guess the parent you replied to would too.