The phrase a simple matter of software has been in common use within the software industry since at least the early 1980s
It is often used as an ironic comment on both the growing importance of software in all human activity and the real difficulty we have in creating good quality software.
However, it is also used without irony to indicate that straightforward software development is all that is required to resolve some issue. This usage is often invoked when the speaker wants to contrast the implied ease of software changes with the suggested greater difficulty of making a hardware change or a change to an industry standard. This non-ironic usage is more often invoked by senior management and hardware engineers, than it is by software engineers.