The PMBOK Guide leaves a lot to your professional discretion and judgment. You and the project team are responsible for thinking through the things it is going to take to deliver a successful project. This is a part of the WBS.
In software, you will somehow need to consider the size if you think its important. Let me give you some examples.
Many years ago while I was in college, the idea of virtual memory was just emerging in operating systems. Our college mainframe had a fixed user space of about 32K (yup ... even your phone has more memory than this today). Professors would leave to work in industry and do research over the summer and find the program they produced couldn't run in our environment. Their planning didn't take that into consideration (but I was available to make it work for them at a fee).
While today's computer has virtual facilities, there are still limitations. You need to identify and plan for these limitations which are essentially risks for your project. Other aspects that may have to be considered as part of software development include the amount of disk storage and transaction rates. If a desired transaction rate is known (e.g. 2,000 simultaneous users minimum for a project I am working on), then you need to incorporate load testing in your up front project plan to assure success.
So the PMBOK Guide may not spell out every step for every industry, however it does suggest risk management and the use of SMEs in project planning. If its important, you need to consider the product size in your planning even if its not stated in the PMBOK Guide.